The question arises whether Bruce's 2010 was the result of a maturing hitter or simply an outlier year. There is evidence on both sides.
Bruce's .366 wOBA in 2010 was driven largely by two factors: 1) a 22% increase in his BABIP relative to his career average, and 2) a 9% inrease in his K% relative to his career average. If we adjust for his career average BABIP, Bruce winds up with a wOBA in 2010 of .313--over 50 points lower than what he actually posted. Adjusting his K% lower based on his career average prior to 2010 only boosts his expected wOBA to .317. So from an outlier perspective the case looks pretty strong given that Bruce's BABIP was 73 points higher than his career average.
If Bruce regresses in terms of his BABIP he'll likely become more volatile as well. Volatility simply refers to his range of performance over any 10-game stretch during the season. In 2010, he had an estimated volatility score of .248, which ranked him about 33rd for batters with >=520 plate appearances. Since BABIP seems to have the largest effect on volatility (I'm still working on the research), a significant regression would not only drive down his wOBA but also the consistency of his performance (volatility of .281 up from .248).
But fear not, Reds fans, there is more to the story. Yes, Bruce's BABIP was up 20% relative to his career average, but that career encompassed only two major league seasons and ~750 plate appearances. Bruce always had high BABIP numbers in the minors and many are projecting him to once again post a solid BABIP (Bill James - .314).
Bruce also made strides in terms of his ability to hit more than just fastballs. According to Fangrahs, Bruce made significant progress in his ability to drive off-speed pitches--well, except for sliders--they still eat him up. (Of course, there is a bit of chicken-and-egg here with BABIP and pitch values).
Moreover, he's making more contact on pitches outside of the zone (53.7%, likely off-speed pitches) and generally getting ahead in the count more often (his first-pitch strike % has decreased from 60.4% to 54.6% since 2008).
If James and others are right, that we can count on Bruce's improvement in BABIP to remain relatively stable, he might regress a bit, but he'll certainly turn in a solid offense year. However, if his BABIP drops back below .300 be prepared for a more average year in 2011.