wasn't Fallout 4 announced just 2-3 months before release?...so it's possible...
5 months actually, really fast, but I would't put that as a norm. I mean, anything is possible, but that doesn't fall in line with how from has announced and released their products, I would say march is way too early.
Still, we don't even know if they are shwoing anything on gamescom, if they aren't there are even lower chances of this releasing so early.