On topic; What are the Borg up to in JJ's universe right now - any speculation? Because of all of the temporal activity in the Alpha quadrant it wouldn't peak their interest?
next movie premise: We know the Borg seek out technology worthy of assimilation. Certainly the Narada's advanced tech, especially since it included 25th century Borg tech would be a very tempting target for the Borg from nuKirk's era. So, the Borg come to the Alpha Quadrant seeking to assimilate the tech from the Narada.