Maybe he creates a villain in order to catalyze the reformation of the Jedi/ "awaken" the Force?
(1) We know Mark Hamill was heavily involved with this film; (2) Harrison Ford is featured prominently in the trailers, but not Hamill; however (3) a mysterious masked villain devoted to Vader takes center stage. Seems too much to be coincidental. It's not as if Abrams is above cliche, after all.
I am also spoiler free, but here is what I think...
The theory seems to fail, if for no other reason, than Mark Hamill is too short (and now fat) to be Kylo Ren. But I also think the pre-movie publicity has explicitly stated that Driver plays Ren, and that there are pictures of him in costume without his mask on.
My theory is:
(1) Kylo Ren is Han and Leia's son, thus a "Skywalker"
(2) He is not encouraged to use the force/there is no one to train him because Luke has become a hermit (like Ben and Yoda, and contra the Jedi who got the universe into a jam)
(3) Kylo ren becomes resentful, thinking that its his destiny to become a Jedi/Sith
(4) The government is a mess, and chaos rules, something needs to be done
(5) He runs away, and/or gets sucked in by some bad guys
(6) He starts to idolize his grandfather as a powerful man brave enough to attempt to bring order to things (5 and 6 may be reversed); order is needed
(7) Luke is called out of hiding to find him once it becomes clear he is working with the bad guys
(8) Luke does not feature prominently until Episode VIII
BONUS: I think Rey is his twin sister, and when he runs away, she ends up with him (kidnapped/stowaway), but she ends up getting abandoned (possibly mind wiped). Why else would she have the swanky accent and say "I'm nobody?"