They already are banned. They were before they were even in existence. The National Firearms Act went into effect in 1934. The first true assault rifle was created in 1942. An assault rifle fires an intermediate cartridge, and has select fire. The civilian lookalikes lack the select fire option.
As for what's going to happen, that's up in the air. Maybe it'll be like the Clinton ban, where it was a matter of cosmetic features, maybe it'll be something worse, maybe it'll falter. I'd recommend you buy at least your lowers and magazines now, however.