Yeah we'll get on Java 8 at some point, hard to say exactly when. Could be soon if all the pieces fall into place just right. One of the big ones is Oracle actually declaring 8 officially the thing to use, you can get it but default is still 7.
They could declare that tomorrow for all I know (heck, they could've done it already, although I don't think that would escape
@shartte's attention) and we could be on 8 within a month. Or it could be delayed some more, but certainly will be within a year, maybe 3-6 months? But that's pretty much a guess
So at this very moment no Java 8 requiring code will be accepted into the main engine branch or the main modules, although Java8 branches or modules could be done if there's a desire to play around with it