The last project I was working on at a major telcom before jumping ship was a project to migrate off of VMware onto KVM systems managed by Cloud Stack, they already have a major Open Stack environment but that's only for SDN stuff now.
We're talking over 10,000 ESXi hosts in the current footprint and at least 50% of them will be off VMware by the end of 2026.
If they were smart, the people they would be focusing on squeezing are the mid-sized shops that don't have the in-house skills or top level cost focus to force a migration. The small shops can't afford to stay on vmware, the very large shops will have the in-house skills or contract to the right people to get moved, it's the mid-sized people that are most stuck.