Not a big fan of the RRHOF, since music is so subjective, but if we look at the criteria for getting in (see below), particularly impact, innovation and influence (not sales or popularity), I would bet on the following getting in.
Pearl Jam - no brainer. Very influential and innovative and very popular to boot - and Vedder's integrity is beyond reproach.
Tupac Shakur - another no brainer, especially as the only real hip-hop act on the list. Tupac influenced a generation of hip-hop artists (and beyond).
The Cars - they helped define New Wave in the late 70s/early 80s and were hugely influential and innovative on MTV, back when they played music videos.
Kraftwerk - If influence and innovation were truly important, they'd be a no brainer also, as they were the godfathers of much of what became industrial/techno/synth and today's EDM music.
Yes - of all the "classic rock" style acts being nominated, which often dominate the inductees, they're certainly the most influential, being in on the ground floor of the prog rock movement - and being the best purveyors of that sound, for many.
Several others should also be considered, like Chic, Joan Baez, Bad Brains, and Depeche Mode, but sadly, I'm worried that popular, but derivative acts like Journey, Janet Jackson and ELO would get in over them and the ones above.
http://www.futurerocklegends.com/Induction_Criteria.php
Nomination and induction into the Hall of Fame is not about popularity, records sales, which label the group is on, or anything other than the process below. The love for, the evaluation of, and the impact of any artist are subjective questions to be answered by the nominators and the voters. Unlike baseball, football, basketball or hockey, statistics are not relevant. Please read below:
The entire nomination and induction process is coordinated by the Rock and Roll Hall of Fame Foundation in New York City. Individuals can be inducted in four categories: Performer, Early Influence, Non-Performer and Side-Men. The only formal criteria for the performance category is that an artist has to have had their first record 25 years ago. That said, candidates are reviewed and discussed relative to their impact on this music that we broadly call rock and roll. The innovation and influence of these artists is also critical. Gold records, number one hits, and million sellers are really not appropriate standards for evaluation.