Seeing Kirk vs the Borg is kinda a cool idea and I'm sure we will see the borg again some day. Maybe in a TNG JJ verse.
I see the Klingons being the villains of the next movie. We haven't seen an all out war with them yet. It's worth exploring. We also got Doomsday machines, killer clouds and a spider-webs floating around too that need to be explored.
Using the Borg this early might be the milk sucking required for the 50th anniversary but it will blow this new Universe's wad if they do it this soon.
Edit: btw, i've had enough of big ships already so another reason why not to do them.