Heh, I've gotta admit this is a first xD. Nobody tends to want Logan to get anyone, mostly because of how he is. Admittedly, he's probably not gonna end up with any of the existing characters, but that's not to say a character won't be introduced specifically for him, who won't stick around long enough for the player to really get attached. No current plans, but I think if he were to end up with someone, it would have to be someone the player hasn't had any opportunity to become attached to.
Also, you can actually collar both Sasha and Riley by the end of 0.22, so we're getting there ;D