That's the operative phrase of course. Sometimes our knowledge gets better.
Yes, but it would be more in keeping with the general tenets of science to speculate what aliens could be zooming around after figuring out if it is even theoretically possible.
If nothing - NOT A DAMN THING among all the waves and/or particles in the universe has ever been seen to travel (convey information, strictly speaking) faster than light, it is no more than wishful thinking to posit that alien spacecraft can. One might as well say they could shrink and expand at will, or change the atoms they are made of.