I agree; Oblivion is one of the three "classic" rides and is very unlikely to be removed. Oblivion serves as a way of drawing the riders of the Smiler away from the queue lines immediately, controlling the lengthy queues inside the long caged area of queue line. Although this may be irrelevant, it is also noticeable that the two vertical sections match each other rather well, serting the tone for this section of the park.
And then of course there is the repaint and refurbishment. Why would Merlin make up a ride thats going to be removed a couple of years down the line? They wouldnt. It is a waste of money, and if anyone likes to avoid loss of profits, its Merlin.
Alton Towers will also be avoiding putting even more work into the X-Sector, making even more congestion into the rather tightly packed space. This would leave two rides left in this section- Smiler and Enterprise. Kbviously, this must be avoided, as there isnt really anything else in that section, discouraging leople to go into that section- defeating the purpose of the 20million pound new rollercoaster.
Credit to NemesisRider for an amazing signature!