Its possible, but if it does happen I think it would take him another year or two than what he projects.
Adrian is a beast, maybe the best pure RB ever IMO, but he has a lot of work to do before he will even be close to rushing record. Emmitt had many special qualities (most notably longevity and consistency) and a ton of talent around him which AP obviously doesn't have the benefit of.
Personally I don't think the record will be broken by AP (this is coming from a guy who would likely take AP over anyone with 1 year to win a SB). It just requires too many things going right for him in the next 5-7 years to make it happen.
I don't think Adrian should take any criticism for this projection. He was just being a good sport an answering the question.
A lot of it has to do with longevity and teams willing to put up with average to below average performance well into a RB's twilight years.
Emmitt is a good example of this -- over his last 5 years (2000 - 2004) in the league he averaged:
878 yards rushing
5.6 TDs
3.8 ypc
Pretty terrible numbers for a half of decade.
Peterson will have to find a team that is willing to accept (like the Cardinals did for Emmitt) an aging veteran RB and be in a odd position that they can't field a competent backup.
Peterson is probably the last RB ever with a chance to best Emmitt's rushing record. With the league going pass happy and running back by commitee the norm, I doubt we see many RBs challenge the record looking forward.
Now, if the league goes to 18 games/season soon, he may have an even more legit shot.
It's unlikely but he's one of those rare athletes that i can see somehow getting there one day.
But so much is dependent on other things, regardless of how special the athlete is. Yes, AP is one of those few that stand out athletically from a league filled with incredible athletes. Randy Moss, Bo Jackson, etc. type players. Luck and circumstance play a huge role though. Bo Jackson had the athleticism, but none of the luck.