Well, if Jane somehow gets the Ring of Life, she can revive some of them. Not Karkat, because she already used it once on him, and I'm assuming Kanaya was completely vaporized, so probably a no go there as well.
But on the other hand, it has been established that John can change things that aren't even meant to be changed (though whether he can actually control that to be anything resembling effective remains to be seen), so that's another option.
couple of edits: Also, Hussie's in comic self said that he didn't know of any timelines where Gamzee died, so that's something to consider.
Also I just wanted to mention how much I love all the artists contributions for this flash, especially Zack Morrison's, because I love his style. btw, if anyone else enjoys his contributions here and on paradoxspace.com, you should check out his comic Paranatural, because it's awesome and a ton of fun. ok that's all for now I think.
edit2: Also, I just realized this might mean we'll get some dialogue between Rose and Roxy, which will surely be awesome.