Do we know if the original hotel will still be playable after the update?

The Original hotel wouldn’t be playable. This is an update we’re speaking about. However, Floor 1 and Floor 2 will be accessible. However, after the revamp. Floor 1 won’t be the same at all nor will the original hotel be playable.

Yes but they may add an additional way to play the original, like a legacy mode

That’d be unlikely since they would have to remake the code and remove many things from it which might not make a legacy mode possible.