They hold a bridge almost in the city. I have no information of when it will begin, but remember the USAF is supporting.
I’d say they are pretty effectively boxed in.
You’re right; most of them will die in Raqqa. Their HQ’s or Caliphate is going to be taken. There still will be cells and danger from them, but they’ll own no land and will be pursued by their many enemies. America haters will attribute super powers to them, but they’re being destroyed.