True, and I hope it remains an exception. With Apple's trend of dropping the optical drive (Air, Mini), hopefully in the 13" Pro laptops they'll use that space to put in a reasonably good dedicated GPU.
I'd hate to see the new 2012 redesigned Pros to be thinner thanks to no optical drive, but nothing taking advantage of that extra space.
I believe that Apple were to go hyper-resolution displays (double what we have now, so 2560 x 1600 on 13"), then they must put in a dedicated GPU in the 13". Integrated Intel graphics simply isn't up to the task. Even if Intel GPU is fast enough to drive the interface, they're not fast enough to drive any worthwhile 3D application (namely games) at that resolution. Considering the Mac App Store is getting more... populated by the day, it only makes sense for Apple to make this move. It'll also draw a nice line between the Pro and the Air.
If apple decides to release a 15" MBA, then I'd say the odds are high that the MBP will retain the optical drive. If we don't hear anything about the MBA from apple, then all bets are off.
I don't think a 15" MBA makes sense. At least not with an aluminum body. I had a 13" MBA, and the thing felt really flimsy. It was... bendy, to say the least. Making the body wider would just make things worse for Apple. Perhaps that was why they scratched the 15" MBA off of the list and went 11.6" + 13" instead.
If the next MBP uses carbon fiber, then perhaps a 15" Air would make sense, but as it is right now, I don't think the 15" Air exists at all.
What I think is likely to happen, is that Apple would remove the OD, spread the motherboard across the extra space, move to flash storage (128GB, 256GB, or 512GB config) as main OS drive and second HDD as data storage, then make the battery flatter. The body can taper down slightly and be a bit thinner, thus making the whole package lighter. I'm expecting something like a 0.9" MBP 15" at 4.8lbs. That'll be a significant saving for Apple, and still makes for a nice update alongside Ivy Bridge and a new GPU.
They can reuse bits and pieces of the Macbook Air, so it'll still converge without making it look like the Pro line is being replaced by the Air.