Originally Posted by Alexrd
I wouldn't have a problem with it if this was set 10 years after RotJ. Since it's 30, the design should be more different in order to show some sort of evolution.
We don't anything about this new X-Wing beyond what it looks like. It might be an older design, or it might be top of the line. In the (I guess now non-canon) background of the original X-Wing was top of the range when the designers defected to the Alliance, and that was just a few years before Yavin.
Lynk's example of the F-18/Super Hornet is a good one - modern Jet fighter design has changed very little since the late 70s and early 80s, both the original F-18, and the even older F-15 are still in use by the US Air Force.