While I thought T3 was a pretty good sci-fi/action film on its own, as you guys have covered in detail, it totally destroyed what was set up in T1 and T2.

T4's only hope is to have Cameron return and focus on the Future War. Then everything could be brought full circle, with Skynet sending the T-800 and T-100 back in time, and John counteracting them with Kyle and his T-800. The film would end with John's musings on finally facing that "unknown future" his mother spoke of all those years ago.

(Oh, and T3 could be more or less ignored.)