Now that I think about it, I think the Felicity theory is a misdirection. As the creators said, they don't even know who's in the grave, so it could be anyone at this point depending on how the story is written. Having it be Felicity is too obvious, especially cutting it to the grave scene right after we get a zoom into the ring. And another poster above made a good assessment that Barry would not be nonchalant about this visit if it was indeed Felicity. I'm 110% sure it's not Laurel, even though if we take comic canon out of the equation, it's retread territory to kill ANOTHER canary on the same show, so I doubt they're going that route again. My best guess is Lance, since him going down this path with Hive already puts him in a questionable moral/series-survival rate position. But then again I was kinda hoping to see a potential story line in which he becomes a mayoral candidate if the Jeri Ryan character doesn't pan out in that direction. Since the flash forward is 6 months from now, we will probably see this scene again as the mid season finale before they go on break and resume the second half of this season's main arc, since that scene has about the same shock value of Ras "killing" Ollie in last season's mid season finale. I sure hope we don't have to wait until episode 18 to find out who it is before going into the climax to end the season.