Since Mirage and 4kids didn't have the rights to the 80's series, Viacom didn't get it during their buyout. If they want the 80's series, it looks like they'll have to buy it from Fred Wolf Films.
Unless they want to own everything related to Teenage Mutant Ninja Turtles, I can't imagine them doing much with the 80's series, since most of the series has already been released on DVD. I guess they could always re-release the DVDs through the Paramount label, or give Lions Gate permission to continue handling the DVDs. If they do want to own everything Ninja Turtles related, I wonder if they're also planning to buy the movies from Warner Brothers.
Speaking of DVDs, I hope that Viacom will re-release the 2003 series on DVD, someday.
As for the Nick series that will be coming out in 2012, I guess I'll wait and see if it'll be any good.