In my opinion, Apple should standardised screen resolutions across models. 13" (Air and Pro) should be 1440*900 (2880*1800 in retina), 15" should be 1680*1050 (3360*2100 in retina) and the 17" (if there ever is one again), should be 1920*1080 (4k in retina).
My only complaints against the present rMBPs is the low effective resolution. My mid-2010 15" MBP with the Hi-Res display is just perfect. My father's 13" rMBP is almost intolerable at 1280*800 scaled resolution. Heck, my father's 9 year old Dell had the same resolution. Scaling to 1440*900 is an option (the only way I use it), but the performance takes a hit and it's definitely not ideal.
Maybe in the next generation...
As for the 17", there is a very small market for such a pro laptop; it's Google Reader all over again (or rather the other way round, since the 17" MBP went first). However, following the Mac Pro's new non-expandable ideology, I'm quite sure that the lack of internal expansion and customisation is not the reason the laptop won't work.
Raptor