Can't say I really care about whether MS drops an ad tier or not. It's the same as the whole Netflix situation for me. I'm never gonna use that low tier, so it's irrelevant to me. As such, I don't have much of an opinion on it. I feel like I very often see people sounding off on these offerings when they're very clearly not even the target audience, and I just don't really get it. Obviously, nobody who's already paying for various premium offerings on service XYZ is going to find an ad-tier of anything particularly appealing. But that's pretty irrelevant at the end of the day.
If I were to put myself in the shoes here, of someone who had to actually weigh the choice of subbing to an ad-tier version of GP for 3 bucks a month, I feel like I'd probably be far more bummed about the 6 month wait for titles than an ad or two playing on boot up. That'll happen once, and then, unless there's a crash, I'd have that game on quick resume until I've beaten it.