May seems like an NLCS kind of option, should they get there. Those middle three games usually require a 4th starter, even if you're throwing him in Game 4 or 5 and just hoping he gets through 3 or 4.
Honestly, the idea of Dusty May (a competent starting pitcher who happens to be somewhere between 4th and 6th best on this staff) having much to do with our playoff performance, either way, seems far-fetched. He's not that kind of guy. So far, he's been...fine in the regular season, which is what you were acquiring him for (and maybe hoping he got really hot and forced you to roster him). There's a lot of factors that we'll end up evaluating that trade on, and May's performance here in August and September is probably the least of the major ones. If he'd shoved (and he still might) in his time here, you could say "good start," but him just being a so-so back-end rotation arm so far is not going to influence my opinion either way.
For me, it really comes down to Romero and Frias/Ragsdale. Romero's the leverage guy you hope can get you big outs in big games (probably in the 5th or 6th), and the other two guys have a low, but reasonable as far as prospects go chance of being impact outfielders. We can all hope the Brewers side of this makes the answer easy, but it probably won't, and it certainly wasn't going to based on 4 Dusty May starts. The answer comes in 2-5 years when we have a better idea of the two OFs.