It actually might be possible that Prim's chances would increase, as it mentioned in book 2 how the children of victor's somehow managed to be more likely to be selected, and thus a reason for victors not to have children. If the Games were rigged (and the books do give a decent thought that they might) it could be that Prim not only might be selected again, but probably would, if not for the 75th Hunger Games result.
I always thought that Prim's selection was through rigging; read the book when it came out, and the first thought I had when I finished was that it was just that; rigged. While I was under the impression that District 12 was home to thousands of people (and I think the first book covered it), the factor of odds would be the same as that one person who bought one ticket for the lottery and won. Prim had her name in the ball once out of how many 12-18 year old children, plus the fact that many had their names in multiple times due to age and tessera. Prim probably had a (I'm guessing) 1:25,000 odds to being selected. I think the contest was rigged since, as we all know, the Hunger Games was just as much a marketing scheme as it was a tool of punishment. Why not, like reality shows, guarentee crowd favorites/personas by 'selecting' a particular type? Such as the District 11 boy who was so big? Or Foxface form 5 (smart/intelligence instead of brute force)?
Makes you think, if District 13 was trying to set up a revolution, was the whole thing a large-scale coup attempt? Was someone like Katness the thing they were planning for and working for? They needed a savior, they just had to wait for one to win?