Will there ever be Kha buffs?

Ever.

Like, ever?

Ever.

I mean, "ever" is a long time. And chances are, the lifetime of League won't be a very significant portion of "ever", even with all of its success. But if you just mean "ever" within the limited life span of League:

Then yeah, probably. The longer the game goes on, the more Champions (and reworks, updates, and overhauls) get released, the more likely that older Champions will get some love. Kha'Zix has been historically been somewhat difficult to balance; how do you make his Isolation mechanics powerful enough to feel rewarding, without being completely oppressive? How do you make countering that mechanic (not being alone) a valuable response without it being so strong that it completely shuts Kha'Zix down? There are definitely some problems with finding the right balance, but I would say it is a safe bet that he will (eventually) see buffs again.