Having not seen anything indicating if there would be a 2013 Corvette Corral at the Baltimore Grand Prix I sent an e-mail to Andretti Motorsports (who ran it last year) and received the following:
Yes, there will be a Corvette car corral again this year. 
Details will be coming soon, so please stay turned to our website, Facebook page and Twitter feed. We’ll be announcing the information through those channels.