The Be'lakor name also seems to be a reference to Kaleb Dark, the first champion of Malal (the long lost 5th Chaos God). If you spell Kaleb backwards you get the beginning of Be'lakor's name.
Be'lakor seems, for all intents and purposes, to reference Malal and Kaleb Dark as an homage to players that were around long enough to remember the old comic...or those who dig up this "secret knowledge".
I personally feel Be'lakor is the demon prince of Kaleb Dark. Demons after all exist outside standard time as such. So even though Kaleb came later, Be'lakor existed for all time as a warrior of Malal (the god that was not to be, due to IP problems)