He's right there on the EU boxart
Although it isn't confirmed, if Cranky Kong is going to be the fourth final character for Donkey Kong Country: Tropical Freeze, Nintendo isn't doing anything to hide that fact -- at least, in Europe they aren't. The European site Nintendo Town has uncovered an updated Amazon Italy listing for Tropical Freeze, and it very clearly depicts the crotchety old kong right on the box next to his co-stars Donkey, Diddy, and Dixie.
Whatever the case may be, Tropical Freeze is expected to be released in a few months, so we'll find out soon enough. As a series fan, I just hope the fourth character brings something new to the table.