I already built three Traitor Knights that I was using the old Apocalypse datasheet rules for, which I can still do anyway - I never play GW events so it doesn't really matter. If we do eventually get updated rules for Chaos Knights, that'd be great but I'm not holding my breath.
Khorne Knight
[URL=http://s105.photobucket.com/user/Allykz666/media/40k%20Khorne/BerserkerKnightTitan001.jpg.html][/URL]
Nurgle Knight
[URL=http://s105.photobucket.com/user/Allykz666/media/Nurgle%2040k/ContagionKnightDone001.jpg.html][/URL]
And the unfinished Slaanesh one.
[URL=http://s105.photobucket.com/user/Allykz666/media/Distortion%20Knight%20Titan%20of%20Slaanesh/DistortKnightSpeakers001_zpsfa26f56f.jpg.html][/URL]
Nothing stopping anyone from having Chaos Knights, as long as you have gaming buddies who are cool with house rules.