Have to bring this thread back to life but I have to throw my hat in the ring on this topic. In terms on non SW rides, Spinball and Rita will most likely be the first to go though the former I suspect will be thr first to go.
In terms of SW rides however, going to be controversial but I'm calling Thirteen to go first and
not Galactica/Air as what everyone else seems to think. It seems the maintenance side of things is why everyone feels that it is doomed and I can see where they are coming from however with technology on these rides always improving to make flying coasters less of a hassle to maintain and if they were to give that ride such a major overhaul a la Nemesis then it would certainly be here to stay.
Also it does prove to be the good step up middle ride from between RMT to Nemesis and regardless what you say, it is still a popular ride.
Anyway for Thirteen, it's downtime and reliability issues makes Galactica look far better in terms of an operation point of view despite being an older ride and with it having such a negative opening if you remember, albeit thanks to marketing at the time, and such a lacklustre outdoor layout which many will point out feels so much like a prototype, it all adds up to the ride looking to be doomed.
Honestly, I wouldn't lose sleep if Thirteen went though if they were to rebuild the whole outdoor layout to be a bit more adventurous to make the most of the surrounding forrest which it fails to do so. Or there is my idea of moving the ride over to Gloomy Wood (with a far different layout there obviously) which is always my personal choice but one that will never happen, them again it wouldn't be the first time Towers have shifted rides around the park...
If there was a rebuild or removal of Thirteen, I wonder if there would be a chance to see Rita get something done with it as this whole retracting with Nemesis if successful might even have the Merlin gimmick machine to go into overdrive with a 'remastered' series with that whole 'they're back bigger and better than before' BS which would go with it. With Nemesis, they might want to 'remaster' Oblivion next with the floorless system and back row facing backwards as some have mentioned already, something with Galactica (return to Air with all that theming that should have been!) And you get the picture.
Though I have said about Rita being likely to go next...I do mean in its current form. Thing with Rita is that I wonder if a retrack program of it might happen in which has a different and improved layout with its launch system modified to be more easier to maintain as if I remember it's layout was hemmed in thanks to Corkscrew being there but with it gone, they might be willing to add a few more features such as a second launch, the odd inversion or maybe make it faster if they want to market it as now being the fastest coaster in the UK?
If Intamin are involved then perhaps some of the footers, mostly in the opening launch section, can still be used to cut down on construction costs like with Nemesis and just imagine a modified Rita and Thirteen interacting through the forrest together creating quite a fun element there. Then again the entire Dark Forrest has to go IMO but that's going off topic, but who's ton say we might see a 'remastered' program with the other SW rides following Nemesis' overhaul?