I am thinking of buying a HD camera, but I still plan to use two very good standard cameras (Sony PD 150 and VX). Supposing I have video from both types and want to put them together in premiere CS5. Will they both fit on the same timeline, etc?
Premiere works fine with a combination of media types in a given timeline.
In case you weren't aware, OnLocation (the forum that you posted on) is a separate program from Premiere Pro. For future PPRO questions, you're more likely to get a response on that product's main forum.