Actually, Kazakhstans is partly within the geographical continent (which some countries taking part now aren't even), and the EBU rules for ESC participation so far doesn't limit the contest to geographical Europe (hence why we have countries that aren't even partly within the continent taking part already).
I do agree though that there should be put a further block of non-European expansion, but since Kazakhstan partly lies within the continent's border, I'd say it would be hypocritical to say no to them and in the meantime accept others that aren't even having a geographical European part.