I think it makes more sense NOT to have a cheap version of the 10" at all. The mini will be the cheap version. So just retina iPad at $500, and mini at $329 (which likely will drop to the more sensible $300 mark).
Nope, I think iPad2 will still exist on their shelves although iPad3 will disappear and leave space for nearly the same 4th gen iPad with lightning (new connector is the ONLY reason to release new ipad).