Should J.R. be back on RAW full time? Absolutely! He gives an air of legitimacy to a very entertainment based product. He never tries to be bigger than the matches or the stars themselves. Moreover, his commentary is specifically designed to highlight the athletes and moves in a very natural, non-forced way. Specifically, he has natural chemistry with Jerry Lawler. That said, not only was it a great moment for J.R. to be back on Raw doing commentary, but it effectively brought Jerry Lawler up a notch as well, as I believe he has been fairly stagnant more times than he's been "on" lately.
Nevertheless I am in NO WAY optimistic about Ross being back on for commentary, either on RAW or Smackdown in even a limited capacity. I completely understand what WWE was trying to do at the old school RAW. That is, throw J.R. fans (and Michael Cole haters by proxy) a bone by putting Ross back on commentary for one night only. That gets those folks talking about how great it would be if WWE put him back full time. That's all fine and good for short term buzz, especially with longtime fans who may not tune in week to week, such as myself.
It's clear that the ultimate goal in that whole segment was to get heel Michael Cole over even more though. J.R. and the King doing commentary took a backseat to Cole talking over them, insulting Ross specifically, and doing everything in his power to take focus off of what was supposed to be a great moment for Ross fans. For anyone who missed it, THAT was the core of the segment... Cole is a jerk, get his heel persona over even more. It wasn't to acredit or even embrace Ross on commentary in the slightest.
Vince and company have worked very hard to get Jim Ross off of the top commentary position for many years now. Regardless of the reasons why, J.R. is now no longer a permanent fixture on RAW (or even the on-air WWE product in general) in essentially any capacity. Unless the McMahons were backed into a very tight corner, there's no way I see them doing an about-face and putting Ross back commentary after all that history.