Prince of Persia 4 haven't been announced...and many don't know about this but if you go on http://www.princeofpersiagame.com/, it will directly take you to a new site: http://prince-of-persia.uk.ubi.com/home.php
This site shows something written and then it comes black slime stuff on the written stuff....Seriously, check it out.
A new Prince of Persia game