Look for a concerted effort to pass gun control legislation this year. The antis in congress would prefer to pass their gun control schemes in 2013.
Many, if not most, voters have short memories. The impact of gun control laws passed this year would be diluted and overshadowed by events come election time in 2014. Not so with gun control laws passed in 2014.
Mid-term elections and presidential elections are two very different things. Turn out for presidential elections is almost always higher because of the publicity surrounding it and because, amongst certain demographics, voting in presidential elections has become the trendy thing to do. Also, four years is a longer period of time that two and thus it gives voters more time to forget a politician's past transgressions.
Mid-term elections, on the other hand, don't recieve near as much publicity as presidential ones and, as such, "low information" voters are much less likely to turn out for mid-terms. In contrast, the people who do
vote in off years are by and large issue voters who are reasonably well informed. Basically, the people who are easily distracted and have short memories do not, by and large, vote in mid-term elections in significant numbers.