I've seen people complain about the transwarp beaming last time for several reasons, one of them being "wahhh, they'll use it for the plot and then forget they have it in the next movie". They obviously didn't. Now, it's "wahhh, Khan's super blood was used as a McGuffin-esque plot device to save Kirk, and woe to everyone if they pick it up again in the next installment. They did the same with the transwarp plot point, how dare they have continuity!".
Seriously, what's up with that? Either you hate it that stuff gets introduced and never mentioned again, or you hate the exact opposite. You can't hate both. It makes no fucking sense.
There's no pleasing some people.
I for one am uber happy they kept him alive, and I hope he and his awesome magic blood get mentioned again in the future. I even hope it becomes a plot point, because the moral implications alone of harvesting someone's blood are incredibly complex.