I think that Wilson will (and should) always be House's best friend, and I don't think a relationship with Cameron really needs to come between them in that respect, any more than House's relationship with Stacy did. You make a good point, though, that the very similarity of Cameron and Wilson might cause House to value or need Cameron less -- only the ways in which she is different from Wilson would cause House to notice her in that respect. Though fortunately for her, being female is a pretty whopping big difference already. :)