i would hope the t4i debuts a new APS-C sensor that addresses the shortcomings of the existing 18MP sensor
also since the entry level is very sales driven based on that all important benchmark of pixels I think canon will need to trump the sony 24MP so i am guessing we will see a 27MP sensor (discalimer this can be taken as CR-3 since i just pulled that number out of my butt)
What are the shortcomings of the current 18 Mpix sensor?
Good point about the megapixel war, but that is so silly.
I feel a jihad coming against me but what the hell

soft images - before i get struck down with vengence and furious anger I say this is relative to the Full frame and APS-H sensors. I REALLY REALLY wanted to get a 7D but when i compared it to my 10MP 1D mk3 it was a no contest the 1D kills it in every way except total pixels and extra reach from the crop.
strange low iso noise - i do pixel peep when editing my shots especially when doing noise reduction lots of people complain about this too
high iso noise - I quite happily shoot at 3200 ISO with both the 5Dmk2 and the 1Dmk3 i would be scared to push above 1600 with the 7D
having said that I got my parents a 600D for xmas and it's good for them they are just learning the whole dslr thing and arent shooting client deliverables and weddings so in this regard the sensor is more than sufficient and handily smashes most point and shoots