Yes, but this will happen, regardless of legislation. The only thing legislation is able to achieve in this space is restrict the technology to actors that are not malicious to begin with.
Yes, this is actually a part of my point. There's no point in legislating it because all it will do is prevent an arbitrary class of people from using it, leaving it only in the hands of people who aren't interested in complying with legislation to begin with.
In other words, it will happen so the best thing we can do is acknowledge this and prepare for it.
Face swap software is only one form of video editing software, and video editing software has been used to deceive people from the moment it was first created. You can easily use adobe aftereffects or blender to deceive people.
Check out the "CaptainDisillusion" channel on youtube, it's full of examples of people deceiving others using video editing software. To my knowledge none of the examples he's talked about have used face swapping.