From a business stand point, they would be missing out on a fantastic opportunity if they simply 'Let it Go'. Frozen is a cash cow with a "if you build it they will come" kind of draw to it, so it makes sense to add it to every park as they have been doing so far. The Maelstrom update is a quick, cheap way to satisfy the Frozen thirst, make tons of money in the process, all the while leaving the possibility of a return of the classic attraction. It really seems like the best move for them right now.
If Frozen doesn't 'thaw', then they will be around when TDO is ready to expand MK again, and in that case, a trackless ride would be a perfect fit.