It's weird, there are lots of artists and musicians who seem to live in both Portland and also many other major cities that are quite a bit more expensive than Portland.  Perhaps you mean everyone who happens to consider themselves an "artist" whether or not they are actually talented and/or good at the business side of art could afford to live in Portland.  In which case, yes, you are correct that Portland is now less affordable for those people.  As would be any environment that starts to get halfway competitive.