I agree. I expect it to be some lone, American-born Muslim goober of Middle Eastern ethnicity, conducting his own personal jihad, quite possibly connected to the Southpark episode.
The only qualifier that I would add is that I'm not necessarily predisposed to believe that it is indeed a "lone-wolf". While that's certainly a possibility, I think it's an equal possibility that there was more than one person involved, only because as I understand it, this man that I referenced has a significant following in the NY area.
I think sometimes we give Al Quaeda too much credit for its "sophistication", and therefor immediately discount people who we would characterize as unsophisticated. In fact, they (Al Quaeda) have been quite crude in some of their attempts on US soil. Yes, the bomb isn't very sophisticated relative to the car bombs found in Afghanistan and Iraq. But, unlike like those places, America is not awash in a sea of readily accessible military-grade explosives, primarily because we haven't been the theater of war for last 6 decades, which is not the case in both those other countries.