I tend to agree, I personally and realistically speaking can't see it moving for some time yet. Without Nemesis, I think Oblivion would possibly take the signature ride position. And given its glittering history and the ride in general it would without question or doubt deserve it!
It takes multiple nerve racking re-rides before the ride becomes numb or it does/did at least for me anyway. The trouble for me now, is just that, it's become numb! The novelty has worn off, and without the novelty factor of the ride, there’s nothing more to it other than the drop. Which isn't all that 'wow' of a feature when the novelty's gone. Whereas on the other hand a roller coaster which has elements and features, still has the elements and features as a solid back up when the novelty where’s off on the said roller coaster. Maybe it's just me being a bit too hardcore with it, or is it?
But consider this. From my experience, out of all the big players at Alton Towers, Oblivion, though it still managers to rack up a fairly big queue on some days. It never nearly gets half as big as what the queue does on the other big boi's at Towers. In fact, I've been on busy hustle and bustle days and the queue's been relatively small considering what it usually would or should be! Realistically though I personally can't see it putting on its coat and walking off for many years yet. But, I do think it is the weakest big ride out of the big rides at Towers, including Spinball Whizzer.