Pro Football Focus looked at touchdown rates for running backs over the last couple years, and a few members of the Green Bay Packers were mentioned. Most running backs don't maintain a high rate of touchdown carries from year to year.
FB John Kuhn ran for a touchdown on 5.6% of his 2010 carries. He was listed as the exception, a running back who might not see his percentage decrease, because he might only see work as a goal line/short yardage back in 2011.
RB Brandon Jackson and RB James Starks had very low touchdown totals based on their amount of carries, and it was so low that it really has no where to go but up. Jackson will probably not remain with the Packers, so it's not clear whether he'll be able to get over 100 carries next season and prove that prediction wrong. But Starks should have over 100 carries next season, and I'd be surprised if he didn't improve on his 2010 total of one (in the NFC Championship game).