just been looking at the codex and FAQ for codex: CSM and it seems to me that the daemon prince is now totally replaceable...
a chaos sorcerer can be T6 (tougher than a prince... )
can have 2 powers (same as a prince)
ca hide in a unit of 3-10 T6 models and thus take less wounds (an average 5 man unit and the sorcerer have 8 wounds, daemon prince has 4)
the unit can carry special weapons for termie killing (the prince has to charge and get his **** kicked)
the sorcerer has a force weapon (the daemon price is just a MC)
so has the mighty daemon prince become "small and mighty" or just a run of the mill "i'll leave it on the shelf to look good" unit