Mercutio already has started thinking of their own such party to overshadow this one, but have made no mention of it, suspecting funds will be lacking, thus no promises should be made, no expectations created.
Pity, though he does express his genuine hope that he shall find the opportunity to visit the Crabbe's, as much as he expects a proposition he must find some way to deflect. If he is to be tied down with marriage, let it be the empress herself, or at least someone interesting like Lady Marthella, the latter being a deal more likely to accomplish, were they not both black sheeps, hmm? Or just his own desire to remember it as such because of some weird feelings, he needed some serving wench to seduce, noble ladies were simply too complicated.