I would be shocked and genuinely disappointed if Brock loses to Cena at the Rumble. If that happens than the ending of the Streak would be nailed on the worst booking decision ever made. Having Taker lose it so Cena can get some more heat would be nonsense.
Lesnar needs to be beaten clean to give a proper Streak rub to whoever beats him. That said; I think they have almost entirely dropped the ball on Lesnar since he won the title as the booking of him has been awful, to put it mildly.
They had him beat the Undertaker cleanly, squash John Cena, then to move onto Cena again, twice?! How about have him go over Orton and maybe bring back someone big(the Rock/Batista for eg.) for a Rumble showdown and have Brock go over him too?
This truly would make it seem as though beating Brock Lesnar is impossible...however, all the while, build 2/3 guys in Upper Midcard feuds who could be seen as possibilities to actually do the job that those Top Guys couldn't.
Was it so hard to book as the WWE made it?
I know there were other factors to take into consideration, but if those couldn't be controlled, then why book Lesnar in the way they did in the first place?