Old version will stay available. Your projects will continue working. Servers will be maintained, kept up and running. But all development will happen only on the new platform.
Hopefully it will be good enough 
to incentivize everyone to migrate, especially considering the fact that code running on hardware will only require minor update.
I’m personally sure you will love it!
Overall, our motivation is not to screw everyone up, but to build a better product, obviously. Also, features we added were requested by community for a while, so I believe everyone will be happy.