actually i think that it should affect price of bitcoin, but not by much, maybe by one or two dollars only as there are lots of people that use bitcoins and steam but that's still not enough
There are only 3 million bitcoin users around the world and there are more than 10million people that used steam. I don't see "not too much" on this number. If 2 million of steam users decided to know and use bitcoin, there's a probability that the price might increase to 50%.