I feel like if Avaya got bought by Microsoft, it would be like Avaya buying Nortel all over again. Two competing products where the buyer (Microsoft) would try to ki-l off Aura to migrate everyone to MS Teams as fast as possible. I think we can all remember how bad it was in those first few years (and even to this day where some of the Nortel folks still say "we wouldn't be in this situation if we just virtualized the CS1000") when it was Avaya Red vs Avaya Blue and all the bad blood on both sides.
Obviously you can connect Teams to Aura via Direct Routing but they can do that with every other PBX and would Microsoft want to support that from a cloud and on prem side (plus all those old versions of CM/CS1000 still in the wild)? If they wanted to buy a call center company, it would make more sense to buy Genesys since their call center can be used on any PBX vs Avaya relaying on CM with CC Elite on top of it (excluding CCaaS Public).
I think it would be very bad for us if they bought Avaya because they would be trying to ki-l Aura as fast as possible to get customers to Teams thus getting rid of those people that support Aura or forcing them to start over and learn the Microsoft Ecosystem. There is no way they would ki-l Teams Calling to move forward with Aura.
It would be better for us if we got acquired by a company that does not do UC/CC today (Oracle, SalesForce, HP, etc) and they move forward with Avaya then migrate as quick as possible.