long answer: two posts from another thread on the topic (Original Topic)
As for the career record, as I'm sure everyone knows, Emmitt Smith currently holds that at 18,355. Peterson currently has 8849 over his first six seasons, through six seasons Smith had 8956, so despite the 2000 yard season, Peterson is still behind Smith's pace. One thing in Peterson's favor is that Smith's production dropped off substantially after his first six seasons. After season 6, Smith averaged 'only' 1044 yards per season the rest of his career and he failed to top 1400 yards in a single season after his sixth after breaking 1400 in five of his first six years, two over 1700, his only low total early was 937 in his rookie year. But, Smith played for 15 years, playing through the age of 35, which is insane for a RB, and before anyone says his two years in Arizona were worthless, he did break 900 yards in his final season. I think it's possible for Peterson, but it'll take him maintaining his current pace for at least a couple more seasons and achieving similar longevity to Smith. Both are difficult propositions, but then again so is a 2000 yard season mere months removed from an ACL tear, so I'm not ready to rule it out for Peterson.
In response to Bay pointing out that Smith had 252 fewer carries through six seasons, with a little more exploration of the numbers:
I'm gonna run a few numbers real quick ignoring Smith's pace and just looking at the total, the baseline number is that Peterson needs 9507 yards to top Smith
he's averaged about 1475 per season so far, if he can maintain that pace (which would be ridiculous) he'd break Smith's record in about 6.4 seasons, so at some point in the 8th game of his 7th season from now, at which point Peterson will be 34 (Smith retired at 35) if we give Peterson all of that 7th season then he'll need to average about 1358 yards per season, which I'm not going to call impossible, but it's tough
if we assume Peterson lasts to the same age as Smith, 35, then he's got another 8 seasons, which would mean he'd need to average about 1188 yards per season, which is manageable, but difficult
another point to consider is that Smith started in the league at 21, Peterson started at 22, but both skipped their senior years of college so I'm going to assume they had close to the same mileage coming into the league, so if Peterson lasts as many years as Smith he'll have 9 more seasons, which would mean he'd need to average 1056 yards per season, which is entirely believable, but has Peterson playing until he's 36
Those numbers don't even get into how ridiculous Peterson's (and Smith's) first six seasons were, it's tough to find comparison stats on that but suffice it to say that averaging 1474.83 (Peterson) or 1492.67 (Smith) yards per season through six seasons is amazing