The existing use cases are well covered by ETH, EOS and TRON. They are not congested by these though, they are congested by gambling and bots.
The concept of steem is not decentralized execution of code. We are lightyears away from having scalability issues. The codebase of steem is the most efficient out there, we are prepared for tens of thousands of transactions per second. Smart contracts would change that, and I strongly doubt the witnesses would take that risk for the chain for something that doesn't cover the mission statement.
EOS runs on steem tech. I don't know what you think you know, but there wouldn't be an upgrade about that. Dan played with the idea of implementing smart contracts, but then moved this to an own project. He took over the codebase of steem, since then there have been several huge updates on steem itself as well as on the code used by both.
I don't know what you understand migrating to mean. So far all info we got was that STEEM would become a TRON token, which would kill off this chain, completely ignore the governance structure of the project, and would by no means be an upgrade! The tech base here is solid, and a move to TRON would never be possible without huge modifications to the TRON core. It would also be too late then to fork off, as a fork would mean forking the current codebase, not TRON.
As soon as this question is out of the room, there is no need for any sort of tribalism. But yes, telling a decentralized community that you will now decide their future will bring people together and make use of the governance tools they have.