It's been quite a losing streak for Marcy Rhoades, the nettlesome neighbor on Fox's Married...With Children. First she was dumped by husband Steve, then had erotic dreams about (blech) Al Bundy (Ed O'Neill), then she had a not-quite-dalliance with 16-year-old Bud. But soon she'll go on a bender and wake up married (to new cast member Ted McGinley). ''It'll work better with two couples,'' says actress Amanda Bearse. ''Marcy was getting too pitiful. And at this point, a change can't hurt.''