It seems reasonable to think the governments will eventually acknowledge there are flying objects whose origins are unknown to them, rather than trying to peddle explanations we're increasing unlikely to believe. I wouldn't expect any acknowledgement of their origins as extra-terrestrial for several reasons, but primarily because that may not be known either. If these objects aren't from any of us, it seems more likely that they originated from Earth somewhere in the future than to think they're interstellar or intergalactic. I'm not convinced we've been visited by any aliens, but if we have, it's more likely they're Earthlings from a distant future. The "grays" people cite could simple be the natural evolution of humans hundreds of thousands of years (or more) from now. There's a lot we still don't know, but at the present, time seems more malleable than distance.