I've owned the 1D3, 5D2, rented the 7D for a week, and now own the 5Dc.
First, in regards to the 1D3 - Awesome camera as long as you get one without any AF issues. Lots of options to set up, AF is great, low-light performance is pretty darn good. You're going to lose pixels-per-duck in relation to your 7D, so if you're doing a lot of cropping (and hence your worries over "only" 10MP, etc) then you might want to stay way. The metering/exposure of the camera can be finnicky at first, especially with flash. Basically, it'll require some practice but typically it's not too hard to rein in this camera.
The 5D2 - Great but sorta "pokey" camera in that if you're used to the 7D responsiveness, you have to slow down a bit with the 5D2 - it CAN do sports, etc, but it's certainly not meant for it: low frame rate, slow mirror blackout, etc. Great landscape and slow-subject, portrait camera, etc. I really enjoyed mine, though I found the highlight rolloff on specular highlights a bit too harsh for me (maybe it was a processing quirk I had in my workflow at the time, unsure)
5Dc - Another great buy IMO, but we're talking bare-bones compared to newer cameras. Rear LCD completely sucks and I only use it to check histograms. No auto-dust cleaning (no big deal to me), no live view (helpful in really careful landscape or macro shooting), etc. But, the image quality is great, so for lots of people that's all they need. I grew pretty used to the "old" configuration, etc. so it's no big deal to me (and actually, the biggest thing that bothers me is the fact you can't change the timer from 10sec!)
In regards to your desire for your full-frame - This thread will probably implode with people claiming they can get great low-light performance with the 7D with some processing, and it seems to be true for the most part (I only rented it for a week so I couldn't fully evaluate it or comment on the 7D's noise performance), so you might want to maybe try some good noise removal software, etc, before commiting to full-frame, though I must say your lens lineup should be okay on a full frame camera (except the 10-20).
As for being concerned with your megapixel count - do you print huge or do a LOT of cropping? If you're cropping a lot, it may be a lens problem. If you're printing very large, you might consider the 5D2 - I have lots of prints from 12MP cameras on 13x19" papers, though, very easy, so I personally don't worry too much with megapixel counts.
I eventually returned to Canon but went 5Dc to focus more money on glass - it's still a great camera.