I don't think so. The best I can remember the Indy 500 starts later than it did the last time Stewart tried the 2 races in 1 day. I don't believe there is enough time between the 2 races to allow for travel. And I don't think you can gamble on not being in Charlotte at the beginning of the race and getting your points.
Nascar's too tough now to run something like Indy. I'm not ruling this out of the equation, but I find it too hard for him to own a team, compete for a championship, and then go off and run Indy and Charlotte on the same day. Just my take
He can run Indy when he's done with Nascar. He can spend the whole month up there practicing, qualifying, etc... I don't see him skipping a points race, especially since he is the team owner.
Tony said a while back that he didn't want to run just Indy. That he owed it to himself and the other comp. to run the whole season and not just show up for 1 race. I bet if the right opp. came across and they moved the time back again he might jump at it though.