The SPS is just another way for Witnesses to feed themselves more

This is utter bullshit. Other than having a SP vote like anyone else, witnesses have no say over what gets funded on SPS. I have little doubt that competent Steem developers, if they wanted to work on Steem, would be funded.

As for the rest, we will have to see. Hosting isn't really an issue. @anyx has already said that his node infrastructure can probably handle the load and could also be expanded (it currently only costs $15/day via SPS).

I think there are a fair number of people involved with Steem who want nothing to do with Tron, but I could be wrong.

Exchanges will follow the user base. If there is a user base on the existing chain, they will support it. If the user base goes away (which was already happening to an extent, and this new development doesn't fix that at all), then they won't.