There is a chance this could help background check legislation. Apparently neither of these guys would have been able to pass one. So if they got their guns from a gun show or via internet sales then that could have big impact. They could start calling it the "Boston Bomber Loophole" or the "Tsarnaev Loophole" and who wants to vote against closing that? (besides Ted Cruz because of 'Freedom' etc)
Uh, no, it won't matter at all, to be honest. 1 person (the MIT cop) dying from a gunshot won't change Congress' mind.