The theories about UW and Oregon moving to the ACC are that UW and Oregon would join the ACC alone, probably without any partners. (At the very most also with Stanford and Cal) It wouldn't be some sort of PAC-ACC merger or non-conference scheduling agreement, as you're seeming to suggest.
There is some question about whether UW and Oregon would be enough for ESPN to re-negotiate its contract with the ACC. (Coupled with issues like the existing ACC members now getting less frequent games against ND with ND's 5 games now being split among 16 rather than 14 members, ACC teams getting less frequent games against other ACC teams who they actually have traditional relationships with, travel costs from adding UO and UW, etc.). But if the PAC as a whole can get such poor TV contract offers, it's even less likely that the ACC could get more money from adding the entirety of the PAC than from just adding UO and UW.