Yeah, track replacing seems to have been pushed aside for now. Whether it was the issues with the previous new piece of track, a shift in strategy or something else that is the reason for that, we'll never know.
I'm not a fan of Colossus - I can tolerate it on the front row (which is the only place I've ridden it in the last 8 or 9 years, and even then, I can count the number of rides I've had on it on one hand). But it does still seem to attract a reasonable crowd and runs reliably enough for now.
But yes, it doesn't quite have the draw of a Nemesis or a Vampire. On the other hand, the park still have plenty of other development spots before they'd have to consider ripping rides out, so Colossus may hang on for a good while yet.
My biggest concern with losing Colossus would be that we would no doubt lose the fun pathway that goes through the ride. Merlin just don't build rides which interact with walkways these days, and I'd be surprised if a potential Colossus replacement has anything beyond a straight pathway running alongside the ride, as opposed to a nice hill or similar.