What's the likelihood of seeing RBE on a front projection DLP unit if I don't see RBE on my current (5 year old) rear projection DLP tv?

Well, its hard to tell, color wheel speeds vary. You know what the color wheel speed is on the RPTV?

No clue. It's a Samsung HLN series DLP.

I would say that 1080p DLP front projectors will have a color wheel speed at least as fast (will be at least 4X) as your 5 year old Samsung rear projector.