I don't think anyone is calling it a sure thing - Jacko is merely predicting an improvement.
He was slightly unlucky last year in some areas, mainly his BABIP and LOB%. But his problem in 2010 (and what was different in this year compared to other years) is his curveball. Here are his curveball run values, according to fangraphs...
2007: 13.9
2008: 13
2009: 16
2010: -3.9
Unfortunately fangraphs doesn't have the horizontal and vertical movement numbers for his curveball in 2010, but I'm willing to bet it's worse. This likely led to more contact on pitches outside the zone (63.7 in 2010 compared to 47.3 career average) which caused less swinging strikes (7.9 compared to 10.1 career average). With this we get less strikeouts (6.99 K/9 compared to 8.23 K/9 career average), and less overall effectiveness.
In a new year, with a new pitching coach, it's possible that AJ can rediscover his curveball, which will likely lead to a significant improvement in 2011.