I know little about Tron, so cannot judge them, but Steem could carry on without Steemit if the witnesses want it to. It's a big community to upset if they mess it up anyway. Interesting that @Splinterlands already uses Tron, so they could easily move over.
Splinterlands uses the Tron token. Moving over to the Tron blockchain wouldn't be so easy. I would sell up, as I don't like Tron.
I am really not sure how this would work. Maybe they do just want dapps like @splinterlands rather than the social side as people do pay money into the game. I have not invested a lot of money in Steem, but others have spent a lot and will be more worried.
Yes it seems most apps on Steem run on custom json which currently tron doesnt support. Their play to actually migrate dApps to Tron is something I hope they touch on tomorrow, as in their current state, it’s not an easy switch.
I expect they could use something other than Steem, but they need to keep it properly decentralised to keep the trust of users. I have heard that Tron is not properly decentralised, but I know little about it.