I think it is debatable HHH / Cena. Taker has never been quite as big, he is very respected among wrestling fans though. I don't think Cena is as big of a mainstream icon as WWE fans think, I'd bet more people still know HHH. Cena is huge among a select group of fans, in a time where wrestling draws far less viewers than during HHH's time. If HHH came back with a vengeance, in great shape, and did something memorable, I think he could regain enough momentum to pull back ahead of Cena, at least for one run. But it's not gonna happen, and it really shouldn't, as HHH has the best interests of the company's future to worry about now, rather than trying to be the biggest star.
I'm not so sure about Cena ever being on Hogan/Austin/Rock Level either. Just because he gets huge pushes and is the centerpiece of the company, doesn't mean he has achieved their status. Wrestling would have to get really hot again, and relevant in mainstream culture for that to happen, and who knows if he will even be the main guy to trigger that, if it happens. It hasn't so far. People like to say he has made all this money compared to those guys, but WWE has undergone a MASSIVE inernational expansion since Cena's been around that has skewed all the numbers. He;s not really in their league. Just like the increased number of PPVs and merch deals, etc skewed Austin and Rock's numbers up in relation to Hogan. As far as star status, 80's Hogan is by far #1, and I don't know if anyone will ever come close, with the amount of options for TV and entertainment available today.