Right, like Quinn is actually going to run. Even if he did, why on earth would the Democrats pick him in a primary? If Kirk is losing by one right now, that doesn't bode well for him. Usually incumbents have leads before the election cycle starts, and then races get more competitive. I'm guessing Kirk will end up the same way Begich did this year. He'll run a strong campaign, and put up a good effort, but Illinois will prove just too Democratic for him, and he'll narrowly lose.
I think it depends,
If the Republicans win the Presidency in 2016 then I would imagine Kirk would pull it out also. Which is in line with what we've seen with vulernable Senate incumbents and Presidential elections over the past decade.
Same goes for Johnson and Reid too.