Big E. Langston's a young guy. He's only 27 year old and hasn't even been on the main roster for a full year. There's potentially plenty of time to do things with Langston later on down the line, barring he suffers injury or garners heat with the powers that be.
I don't see WWE turning the guy into a clown and I wouldn't exactly say that he's been "built" up to any real degree. His role thus far has been the bodyguard of Dolph Ziggler & AJ, then just the bodyguard of AJ while feuding with Ziggler. He's not been a focal point in any sort of major way right now and has been exactly where he belongs at this stage in his career: firmly in the mid-card.
Besides, WWE reportedly had it planned for Langston to feud with Mark Henry over the course of the summer, with the feud culminating at SummerSlam in either on final match or a possible strongman contest. But, Henry's been injured and there's been all sorts of questions & rumor regarding him having heat due to questionable toughness. Quite possibly, WWE took a look at the lay of the land and figured that they wanted everyone else doing what they're currently doing. As for whatever feuds were left, would people honestly care about seeing Langston feud with Zack Ryder? How about Justin Gabriel? Would they wanna see him in some pointless endeavor with The Great Khali and Hornswoggle? I know I certainly wouldn't. So if they wanna keep him off TV for a while until some storylines pop up and the lay of the land to change so he can be put into some sort of remotely relevant program, then I've got no complaints.