Nash's MVP seasons were VERY weak, and really shouldn't set a precedent for what a PG needs to do to win MVP since
a. Chris Paul has had better PG seasons offensively than either of Nash's years, and
b. Paul did so while also playing more minutes and way way better defense (as in good defense rather than well below average defense).
Unfortunately, Nash's sentiment and media driven MVPs have kind of skewed what it seems like a PG needs to do to be in the MVP discussion.
Rondo has been playing really really well, and is averaging 11.6 points, 16.4 assists, 2.6 steals, 6.0 rebounds, 4.0 turnovers. So to be in the discussion, he is going to need to basically keep his steals, assists, and rebounds where they are AND increase his scoring up to about 15.o at least while decreasing the TOs...which is a huge jump considering he is already playing the best he's ever played. That, or he's going to have to get his scoring up to 18 or so and keep his assists at 13 or so all while maintaining all-defense recognition. Hard to see that happening this year, unfortunately.
For example, the following was NOT an MVP season by a PG:
21.1 pts, 4.0 rbs, 11.6 assists, 2.5 TO's, 2.7 steals, .488 FG, .369 3p, .851 FT.; 56 wins
That was beaten out by an SG with
28.3 pts, 6.3 rbs, 5.4 assists, 3.1 TO's, 1.8 steals, .459 FG, .361 3p, .840 FT.; 57 wins (w/ better teammates)
Point being, Unless you can garner the media blind devotion that Nash does, a PG will rarely beat the SG/SF type unless it's ridiculously phenomenal.