I'm sure it wont, it looks like it'll be far easier to make something worth watching than using Gmod. There won't be any of that flailing arm shit there is from Gmod.
Rewatching the SFM intro video, they talk about the workshop being constantly filled with new set pieces for film makers. Wonder if that means purely items, or they're going to consider adding maps to it? Hate to bring this old debate up again, considering I don't think they will, but this is the best supporting argument for the idea I've ever heard.