I agree in that I could see Microsoft pursuing an "always online" requirement if they're working in tandem with one or more internet service providers (to become the new cable box), as well as one or more major publishers who are intent on curtailing used games. I think there were past rumors about Microsoft trying to get deals with ISPs, and there was also a recent rumor about Microsoft possibly reaching an exclusive deal with EA (who themselves have experimented with always online functionality), so many of the rumors seem to be pointing towards the "always online" direction.
I always thought that Microsoft couldn't block used games without Sony or Nintendo doing so as well, but perhaps they could do it with ISPs and publishers. This could also force Sony's hand to implement their patent if publishers support the blocking of used games. Or it could push core gamers onto the Wii U, PS4, PC, or other platforms.