For your price range, I'd suggest the Nikon d7000 over the 60d
Choosing Nikon or Canon is a tough decision, and the d7000 has the better specs. But it is more expensive, too, I like Canon usability better and Nikon doesn't run magic lantern - that's why I got Canon when I had to decide 1.5 years ago.
The 60D is a great camera coming from P&S cameras, but the T4i is going to be a super shooter if they put DigicV in it.
Omg - an upgraded cpu won't fix your sensor but maybe noise-reduction in jpeg, and the t4i most probably won't have a new one. I have a 60d and wouldn't want to get a xxxd because the ergonomics of the 60d are much better (back dial, top lcd display, buttons). When you're advancing in photography, better usability becomes more and more important.
I would seriously consider the 15-85 over the 18-135 for IQ reasons. Also the 15-85 is a bit wider making it 24mm (FF equivalent) which is great for landscapes and the build quality is better. Both have the same variable apertures so that is a wash.
+1 ... cropping from a shorter good lens is better than having blurred pictures at longer range.
Second, hold off on the 55-250 until you have had time to learn your camera and body. Chances are very likely that you will want a higher IQ lens than the 55-250 and you may discover that you might want a different focal length.
+1 ... face it, a usable tele lens will cost you, or you'd better crop from a shorter one (see above).
There really is a big difference between f4 and f2.8. It could mean the difference between using flash or not.
Imho f2.8 is overrated, it's not that large a difference, for "shoot in the dark" look at f1.4 and the like. The good thing about f2.8 is that the af works better in low light, but a larger aperture is meant for shallower depth of field (and even f4 is quite shallow) and cannot fix up a sensor's noise problems nor replace flash.
You should also budget for a separate flash.
Yep, but for starting off the built-in flash is surprisingly ok because the 60d has x-sync up to 1/250s.