Are there any plans to remove support for SSMv2 at a future date? I don't see that written anywhere but just wanted to confirm as I do see you are encouraging new customers to use SSMv3.
Release : 14.0
There are no plans to remove support for SSMV2. In fact, even with SSMV3, the code that actually does the job is the same as in SSMV2.
SSMV3 provides basically an interface for manipulating the resource and action tables and also some facilities like dynamically created rules to detect state changes and the creation of multiple policies. However, in the end, what causes products to be monitored and acted upon are the resource and action tables as in SSMV2.