If we are looking at 2014 as a comparison (we all want that offense, not the one of the last two years), he had 2834 yards passing in less than 12 games. He was averaging around 240 yards passing per game. I think that would be a good target, and would give him 2880 through just the regular season. Counting a conference championship and/or bowl/playoff games, he should clear 3000 easily, provided he stays healthy the whole season and we see the progress we are all anticipating/expecting. Over on that. (same thoughts for passing TDs - he had 34 that year in under 12 games).
Rushing yards, though.. He had over 900 back in 2014, but I'm not sold he will run as much. Especially in games that aren't close. I see at least 5 games that probably won't be close, and it's a safe bet that one or two of the others that maybe should be closer, won't actually be close. That being said, I'd have to take the under if forced to, although 900 is possible.
I think we would want to see 3,500-4,000 yards of offense total from JT if we are going to see a significant improvement from the offense. He had 3,400 last year, and 3,772 in 2014. May not seem like much of a difference over the course of a season, but he also had 13 full games last year and less than 12 in 2014. So he averaged over 320 yards/game of offense in 2014, compared to 260 yards/game last year. *If* they play in 15 games, that pace (2014) would put him closer to 5,000 yards of offense. Time will tell.