Even if he gets indicted, all Rove needs to do is to run out the clock until one day after the '08 election. Then its pardon time. If McCain is the GOP candidate, Bush might not even wait that long. It will be two-for: a going away gift for a loyal soldier and a kidney punch to a disloyal one.
With this trumped up Earle prosecution of DeLay going on, I think that indicting Rove would be a very big risk unless they have some pretty good evidence against him.