No upgrades to the 4.2 Vortec yet, and I wouldn't hold my breath...GM would probably go the V8 route if they need to come up with 400 HP for an SUV.
But I did have a lengthy conversation with a certain master engine builder in CA who has done a lot of work on the 4.2 for street rod use. He has resolved the EFI harness issues and also the oil pan concerns. Now, all we have to do is convince him to find the time to write up his results for the "12 Port News"! It will happen, just not sure when...