The investigation into Michael Vick's possible involvement with dogfighting is not going away and, in fact, seems to be picking up steam. Investigators in Virginia are checking the stories of informants who may link Vick to the animal cruelty that might have occurred at a property he used to own.
It is possible that prosecutors will have enough evidence to put before a specially convened grand jury in July, which, as the NFL calendar tells us, is training camp time, and that has to make the Falcons uncomfortable about their QB situation. There's a lot yet to be sorted out, not the least of which is whether Vick actually did anything wrong. And legal proceedings could also be delayed until after the season (which we all know is the most important thing -- we wouldn't want anything as petty as a criminal case to interfere with the season).
Until a few months ago, the Falcons had arguably the best quarterback security blanket in the league in backup Matt Schaub. Of course, he was traded in March to Houston.