Summary: Most enterprises haven’t fully moved to cloud voice. While Teams Phone adoption is growing fast, legacy PBXs persist due to complexity, compliance, and coexistence needs. This data-backed article explores why PBX systems still have a stronghold, how Microsoft Teams fits into a hybrid model, and what IT leaders can do to modernize voice architecture without disruption.
You’d be forgiven for thinking everyone’s already moved to the cloud. Attend any keynote and the message is loud: Teams Phone is booming, AI is transforming the contact center, and PBXs are a relic of the past.
Except they’re not.
While cloud voice adoption is accelerating, the full migration picture is far more nuanced. Only 10% of European enterprises were fully cloud-based in early 2024, and 92% expect to manage hybrid environments combining cloud and on-prem infrastructure through 2026 (Frost & Sullivan, UCaaS in Europe).
That’s not a stall. It’s a signal. Beneath the surface of all the Teams momentum is a market that’s still very much in transition. Enterprises haven’t finished migrating. Many haven’t started. And for IT leaders, that gap is the reality you have to manage and fix.
The cloud hype vs. the hybrid reality
Microsoft Teams has become the world’s leading business telephony platform, with over 20 million active Teams Phone users as of 2024 (Frost & Sullivan, Growth Opportunities in Microsoft Teams). But for global, multi-site organizations — especially those in regulated industries — most deployments are partial.
Only 10% of enterprises have gone fully cloud, and the rest are on phased or hybrid migration paths (Frost & Sullivan, UCaaS in Europe).
Microsoft’s dominance is clear: it now captures 46% of the global UC&C market, generating $31.5 billion in revenue, with 14% year-over-year growth. But coexistence remains the norm, not the exception.
The barriers to full migration include:
- Global operations with region-specific requirements
- Legacy hardware and workflows
- Regulatory compliance needs
- Unfinished Contact Center integrations
- Fragmented vendor environments
Industry pace varies too — finance, manufacturing, and public sector organizations face heavier constraints than tech or retail (Frost & Sullivan, UCaaS in Europe).
As Mike Nowak, General Manager of BCM One Enterprise Solutions shared at Commsverse 2025:
We’re powering both on-premise and Teams Operator Connect at the same time. That’s what customers need, not a rip-and-replace pitch, but a real plan.”
Why the PBX still has a pulse
Most IT leaders want to get to the cloud. But it’s not a simple decision.
PBXs are still in place because enterprises need:
- Call recording that meets industry standards
- Redundancy for branch or remote sites
- Analog support for devices still in use
- Voice workflows that match how users work across platforms
Many PBXs were deployed on 15–25 year lifecycles and are deeply embedded in business operations (Frost & Sullivan, Growth Opportunities in UCaaS). Displacing them means untangling systems, contracts, and user behavior — all while maintaining uptime.
Even in forward-looking Teams Phone deployments, Direct Routing, local SBCs and hybrid setups are often still required.
The result: hybrid voice environments persist longer than expected.
The shift in voice expectations
Voice is no longer a silo. It’s a strategic capability with broader enterprise impact.
Enterprises expect voice services to include:
- Global number management
- Platform coexistence (Teams, Zoom, Webex)
- Integrated contact center support
- Monitoring, analytics, and visibility
- A single provider that can manage the complexity
Voice also needs to work for frontline and mobile workers, not just office users. That means supporting BYOD, app-free calling, and compliance-ready mobility (Frost & Sullivan, UCaaS in Europe).
Even with Teams in the lead, over 55% of enterprises still manage multiple collaboration platforms (UCMarketing, State of Microsoft Teams 2025). According to IDC, Zoom controls 6.2% of the market and Cisco 5.3% — coexistence is a permanent operating model, not a transitional state.
You can’t just offer voice in a vacuum anymore.”
– Mike Nowak, General Manager, BCM One Enterprise Solutions
Contact Center and AI: The next battleground
AI-driven contact centers were a hot topic at Commsverse. And the data shows why:
- 88% of IT leaders say AI is important to business goals
- Only 20% have deployed AI at scale
- 73% cite ROI and data complexity as barriers
(Frost & Sullivan, Growth Opportunities in UCaaS)
Real-time agent assist, AI-based routing, and speech analytics depend on clean, integrated voice infrastructure. If you’re still on siloed PBXs or inconsistent vendor stacks, your AI plans will stall before they start.
Modernizing voice is foundational to modernizing the contact center.
Don’t ignore vendor risk
Microsoft now owns nearly half the UC&C market. That scale brings efficiency — but also risk.
- The EU has launched an antitrust probe into Teams’ bundling with Office 365
- A global outage tied to a third-party security update in 2024 showed the fragility of relying on one stack for meetings, calling, and analytics
Avoiding single-vendor dependency isn’t just a procurement concern. It’s a resilience issue.
What IT leaders should do next
Your 5-step action plan
- Inventory
Map PBX locations, device dependencies, compliance obligations, and carrier contracts. - Prioritize
Identify which regions or departments are ready for Operator Connect or Webex Calling — and where hybrid needs remain. - Bundle
Include call recording, analytics, and global number management from the start. Don’t treat them as bolt-ons. - Choose
Pick a partner who can deliver hybrid voice, not just cloud-native solutions. - Plan
Expect a long tail. Build in governance, support, training, and ongoing monitoring from the outset.
The future of enterprise voice isn’t a platform. It’s an architecture.”
– Mike Nowak, General Manager, BCM One Enterprise Solutions
Final word
Cloud voice adoption is real - but so is the inertia of legacy systems. With only 10% of European enterprises fully cloud-based, and 92% managing hybrid through 2026, Teams might be leading the race, but the course is far from over.
The enterprises that succeed won’t be the ones with the most licenses. They’ll be the ones with the clearest roadmap, the right architectural foundation, and partners who understand the operational realities of coexistence.
That’s where we come in. Pure IP Enterprise Voice design and manage voice architectures that fit the real-world complexity of large organizations.
Whether you’re integrating Teams into a legacy environment, building coexistence across platforms, or adding industry-specific capabilities like compliance recording or analog support, we understand what it takes to move without disruption.
If you're planning the next phase of your migration, let's talk about what success looks like in your environment.
