They have always been giving FM (and FITH) TLC as they go along. Sometimes it's small things, sometimes it's obvious. I still don't think some posters here appreciate it enough when they talk about it getting "run down". It's simply a classic attraction, and of course it was a lot more awesome when you remember it 20 years or more ago because everything is 10x better in retrospect. It's still one of the best dark rides in the nation, and I really mean that. Like I've said, most of the other classic dark rides at places like Frontier City and Carowinds have been replaced with crappy modern renditions with cardboard cut-outs instead of props. I've ridden FM countless times over the past couple decades and I'm still always seeing new details that I never noticed before.
Anyway, I've been thinking more about the original question, and I think that whenever FM does finally go, the park will indeed probably announce it as the final year. I assume they'll hype up a replacement at the same time, similar to how Carowinds just did with Thunder Road. I still want to believe that any replacement would simply be a revamped dark ride experience though, hopefully of the same theme and nature. I don't think prisoners are PC enough for them anymore though... they'd probably go with flood rescue operation theme or something with it's own custom monument in front