Don't know if this is a repeat... But I just saw that Glock is getting ready to release official Generation 4 pistols (not just RTF's), that will include ambidextrous slide/magazine releases, and interchangeable back straps. Thought it was interesting... We'll see.
http://www.gunsholstersandgear.com/2009/10/29/gen-4-glock-a-look-at-the-new-features/