No, absolutely not. That's averaging, over the course of a season, even more than LJ averaged over the second half of last year (156.25 yards per game). Johnson didn't have any bad games last year; just one bad game all season makes 2500 yards impossible. Let alone staying healthy for that kind of workload.
He has a realistic shot at 2000 yards, depending on what happens with the team in 2006. If you look at the backs who've rushed for 2000 yards, there are some team similarities
Passing offense:
Buffalo 1973 (OJ): #26 of 26 in pass completions, attempts, yardage, TDs.
Rams 1974 (Dickerson): #28 of 28 in pass completions, attempts, yardage, #23 in TDs.
Detroit 1997 (Sanders): #11 in yardage, #18 in TDs.
Baltimore 2003 (Lewis): #32 of 32 in completions, attempts, yardage, #26 in TDs.
Defense:
Buffalo: #10 in points allowed, #14 in yardage allowed, #10 in rushing yards per attempt against
Rams: #13 in points allowed, #13 in yardage allowed, #3 in rushing yards per attempt against
Detroit: #10 in points allowed, #14 in yardage allowed, #14 in rushing yards per attempt against
Baltimore: #6 in points allowed, #4 in yardage allowed, #3 in rushing yards per attempt against
Barry Sanders' year was different than the others, and for that matter he's a different kind of runner than the others. Johnson is much more similar to OJ, Dickerson and Lewis than he is to Sanders. The 2000-yard seasons for those backs required a pathetic pass offense, and a good defense, particularly in rushing yards per attempt against (important, I would estimate, because a good run defense lengthens the game, giving your rushing offense more attempts).
KC has had a top-5 passing offense for the past three years, and has had a bottom-half run defense over the same period of time. I do not think it's likely that Johnson will reach 2000 yards if those two factors remain the same. If there is a Trent Green or Tony Gonzalez injury, and the run defense improves, he may be put in a position to reach 2000 yards (or even Dickerson's record).
I felt obligated to respond to this and do some research of my own (with no preconceived notions). Here are stats from his 9 games as a starting back and the corresponding passing and defense numbers.Passing; Defense
22/35 235 TD; 23PA, Sack, INT
23/40 220 3INT; 14PA, 2Sack, 2FF
19/29 220 3TD, INT; 17PA, Sack, INT, 2FF
19/26 323 TD; 16PA, 3Sack, 4INT, FF
16/23 253 2TD, 2INT; 27PA, 2Sack, 2INT
20/32 340 TD; 31PA, 4Sack, FF
15/28 176 INT; 27PA, Sack, INT, FF
19/35 207 2TD; 7PA, Sack, INT
23/29 344 TD; 3PA, Sack, 2INT
Total: 176/277 2318 11TD, 4INT; 165PA, 15Sack, 12INT, 7FF
Avg: 19.6/30.7 1.2TD, .4INT; 18.3PA, 1.7Sack, 1.3INT, .8FF
Adj.Season: 313/492 4121 20TD, 7INT; 293PA, 27Sack, 21INT, 12FF
Adj.Passing Offense Rank: 2nd
Adj.Defensive Scoring Rank: T-9th
Actual Passing Offense Rank: 6th
Actual Defensive Scoring Rank: 16th
Johnson Totals as a Starter: 261 1351 16TD 5.2avg, 27 276 TD 10.2avg
Adj.Johnson Totals: 464 2402 28TD, 48 491 2TD
Now, it seems to me that if you think about it.... Johnson would be slated to have a Barry Sanders-type 2000+ yard year. A good passing offense and a pretty good defense. Throw in the fact that he's a receiving threat (like Barry Sanders, 33 305 3TDs in 1997), and
I'd say he's reasonably capable of breaking 2500 yards from scrimmage, but not 2500 rushing yards.
If Johnson does ever break 2500 rushing yards or come near it, it will be in 2006 and 2006 only, because he'll never in his career ever have a better offensive line or full back or overall situation to accomplish this feat.
For what it's worth, Shaun Alexander is in a very similar position to do that in Seattle, but unlike Johnson, probably will have that opportunity for each of the next 3-5 years.