Addon SDK v2; Better video support; Prompt on close & lots more.
By creating a compatibility disaster ruining EVERY customer's project ?
I'm using 4 years old add-ons and it's fine. If one break by accident, it's likely it would be fixable in some way by renaming a function or rewriting a little chunk of the code.
But soon, EVERY addon will break, EVERY addon will need to be rewritten from scratch and some of them (all the best ones) won't be possible to port.
Customer projects will continue working fine if addon developers co-operate and update their addons to the SDK v2.