Considering that...
-Donkey Kong's been by himself in the last two SSB games
-Diddy's been in various Mario sports games even since Rare went Microsoft
-Many would say it's about time that another Donkey Kong character got into Smash...
I always thought that it was only a matter of time before Diddy Kong got confirmed. Glad to see it's over and done now so that his biggest fans won't have to worry anymore. I'm not one of his biggest fans, but I'm glad to see that he made it.
He should have some cool jetpack attacks, but wouldn't it be kind of funny if (since it's uncertain if he's using his legs or tail to attack Link in that screenshot, though I'm leaning on 'tail' a little) all of his tail attacks were direct clones of what Yoshi did in SSBM? Not that it should happen, though; in fact it's safe to say that they'll make him a unique playable character in almost all aspects.
As to whether or not he might use a variation of the Giant Punch for a Special Move, somehow I think it could go either way...but I'm sort of leaning on 'perhaps not', though it'd be amusing to see him using his own version.