Depending on how long Bryan will be out of action, The Shield are three guys that I don't think the company can do without at this period of time without leaving a huge gap. Their match at Extreme Rules stole the show and they've definitely been made the primary focus in Bryan's absence. Don't get me wrong when it comes to Cena. In spite of whatever hate Cena gets from various smarks, don't let that fool you into think that Cena isn't popular with a healthy majority of WWE's audience. If Cena didn't draw or generate money, he wouldn't be in the spot he has. However, despite his popularity, you have to get the feeling that people are also just downright burned out when it comes to John Cena. He's been on top for such a long time, he's been strongly booked with more consistency than any wrestler in WWE since Hulk Hogan and his ultimate good guy character has had very little growth for close to a decade that people can't help but be a little tired of him.
One reason why fans have gravitated to Bryan and The Shield is because they're still extremely fresh. It also helps that they're consistently putting on high quality matches and aren't booked to look like indestructible supermen embodying the term juggernaut. Cena being out for a while could very well deliver a blow to WWE's numbers for the short term but, frankly, I do think that Vince puts even more faith in John Cena than even Cena's worth. WWE survived when Hulk Hogan, Ultimate Warrior, Bret Hart, Stone Cold Steve Austin and The Rock all left; they'll be able to get by just fine in the long run if Cena winds up being put on the shelf for a while. I also think they'd get by without The Shield as well but, as I said, The Shield are fresh in most people's eyes whereas a lot of people are bored with Cena. WWE'd get by without The Shield, but it'd be a lot more boring for a while.