First about Grodd.
I don't think this is the real Grodd exactly, or perhaps more accurately not the final Grodd. Let me Explain.
This Grodd was still too dumb to me, maybe that's because it's still his Origin, but I don't know.
Many people may be upset about removing Ape City in exchange for making Grodd another product of the Accelerator. But here is my idea.
I think this Grodd will somehow get time traveled back to the distant past and become the founder of Ape City. And then in a future season from that will come the proper Grodd. Someone named after the City's founder.
Now unto Eddie Thawn. I do not believe he will become Cobalt Blue, I think all HGobard's talk about him being "almost completely forgotten" says he's not a big player.
Question is, if he is such a failure, what's the one thing that left him still a little remembered? Many are remembered only for being the Lover of someone far more important.
I think Cobalt Blue will as usual be Barry's twin, but this time it's a female twin. And she becomes Eddie's future Wife and also ancestor of Eobard.
One more thing, I ship SnowWest now.