Nah I'm not going for the Silver = future Gray. I never liked time travel stuff and I certainly wasn't very keen on the whole time travel business during the GMG arc as it still doesn't really make much sense. In the end though Hiro implied that in fact all the time travel was part of a larger linear line, meaning that any messing with the flow of time was already in calculated. He did this with Zirconis who originally introduced himself as the Jade Dragon when Wendy resurrected his spirit while he only picked up the title for the first time just before he was sent back to the past. This was later partially implied again when Atlas Flame said 400 years or something had been passed since they first met.
Having yet another time traveller to the mix, now that would just be a pain, especially because Silver should have been almost half his life living in the past, with other words he lived a long time simultaneously with his own past self, which he apparently loathes? Then you also have the mysterious grave. You would think that someone who went that far in the past, way before whatever changed him happened, would try to change whatever would come to pass. Well it's possible he is actually doing that, but then why the self hate for his past self?
It's just too confusing. I mean something happens in the future that made him hate himself, goes back to the past to...hate himself some more? Also wouldn't future Gray have known about Atlas Flame? Still he thought he was a demon and Silver was quite late with the Natsu comment. Overall his actions don't really mix with how you would expect a future Gray would act, even if he turned evil.
Maybe that's why he's wearing armour ~_~