According to GM Inside News, both trademarks are dated April 27 and are simply described to the US Patent and Trademark Office as being for "motor land vehicles, namely, automobiles." That doesn't narrow things down at all. However, since the moniker is specifically for both sedans, Sport Touring might be a new trim or special edition for them. Buick had no comment when reached by Autoblog.
Of course, there are a whole host of automotive trademarks that are claimed that end up with no actual vehicle in showrooms. Unfortunately, we just have to wait to find out if this is another case like the Buick Enclave Tuscan where the filing offers a preview of the future or a situation like the still long-awaited return of the Supra.