Arlovski is not moving down to 205 lol. If he does, that'd be some shit but it ain't happening.
I agree sometime we'll see Arlovski-Sylvia 4. Arlovski is the only credible challenger for Sylvia they got. Once Monson gets his shot, people will realize how far off the UFC's "top HW contenders" are to Sylvia and Arlovski for that matter. So basically it's just a matter of time until Arlovski earns a fourth fight, and call me crazy - I'd still pick him to win against Sylvia if they fought again.