Cena, for all his faults, is a strong, muscular dude. There are dozens of examples that can be pointed to when discussing his strength (around 85 involve him performing his finishing move on Big Show). His aversion to selling is incredibly well documented. That Big E was allowed to blast Cena like a jobber was the best possible debut for him. It has been shown that he can best the top guy in the company.
Of course this treatment can't last. SuperCena is bound to cease with the generosity sooner rather than later, at which point he will treat Langston like everyone else on the roster. That is to say like fodder for the supremely powerful valiant babyface.
Big E should make the most of the time he has before that occurs. Being put into a unit with the intriguing-once-more AJ Lee character and rising star Dolph Ziggler has placed the NXT champion into a very good spot on the card. He's with two performers that guarantee him regular appearances on TV and there’s next to no pressure on him. He can loll about being a charisma vacuum all he wants, as long as he grimaces at the right moments management are unlikely to care.
No ridiculous comeback here
Big E should make developing some sort of personality a priority. While it's clear promos will never be his strong point (big muscles are his thing) he needs to master the basics if he's to advance beyond his current role. He'll want to do that too, 'The Show Off' won't need a bodyguard forever. Having watched him since his debut in NXT I know this is an area that the big man needs to improve.
A big showdown with Cena seems likely. If it doesn't happen on RAW's 20th Anniversary Show then the Royal Rumble would seem the logical place for that match to occur. Perhaps Cena will surprise us and remain generous in his interactions with Langston. If he does and Big E manages to get a win over the leading man, tainted or otherwise, that would keep the newcomer on the path to success.
His debut has been timed and handled well. If WWE hope to mould Langston into a greater talent capable of attracting and entertaining fans they have a lot of work to do. Pitting him against Cena is a nice start. But it's just that: a start.