Although many people refuse to accept it, The Smiler is the only rollercoaster to be on par, if not better than Nemesis to people and it's creator. Currently it's the park's biggest draw, even with Galactica, people still go to ride The Smiler - granted not everybody
but still a large chunk.
On top of this, people seem to forget this is the biggest investment Alton Towers have made, not to mention all the extra money it's meant them having to pay out in the long run.
The Smiler has once again shocked people again this season, with many Nemesis fans moving toward it due to it being improved vastly, so in reality the uproar would be at least as bad as Nemesis if the ride was removed too quickly.
People seem to to think that just because it's made me by Gerstlauer it won't last? I have never understood this as they are made out of the exact same thing as any other ride manufacturer, like said above, with the ride being the smoothest it's ever been this year it's certainly proved it ages well.
The ride itself has the most tech I've ever seen any rollercoaster have, I'm sure they wouldn't invest in something of its calibre if they planned to remove it after it operates for the same amount of time as Rita.
Finally, why would they? It's a huge roller coaster that really shouldn't be at Alton Towers due to their restrictions, but it is. Why would Merlin throw that away to replace it with something smaller when restrictions could be tighter in the future?
That's my thoughts on the matter anyway, I don't see The Smiler going anywhere for a very long time yet and I feel it may surprise people with how well in ages.