It is a possibility that somebody else (probably a state) will come in and buy us outright later on. But it's more likely that Ratcliffe will be the one doing it. It'll cost him less than it would any state. He'll already have at least 29% of the club, and chances are it'll be higher than that as the Glazers will likely issue further shares to him for further investment. They won't allow him majority control by doing that, but it's likely they'll happily let him increase it a fair bit more yet (bearing in mind that if his investments increase the value of the club, it'll be increasing the value of their shares).
As others have said, every other state has bought a smaller club and spent money to make them successful. It both works out cheaper that way and makes them more synonymous with that clubs brand. Using that same thinking now, it's more likely that a state would have preferred to buy us when we were down and then been the ones to turn us around, rather than just buying the finished product in the future. That's not to say it won't happen. Perhaps one of the states wants to do it differently this time. Perhaps the state wasn't in a position to buy now but will be in a few years. Things change. But based on what has happened before it is the lesser likelihood.
I'm pretty sure that redNation is actually right on this, and only the original 300m investment is guaranteed for that. It's then left open that future investment might be treated the same, but it would have to be agreed on by the Glazers in a separate discussion (and I presume it wouldn't necessarily be for $33 a share). What I'm not sure about is whether all the Glazers would have to agree, whether a majority of the Glazers would have to agree, or whether a majority of the owners (so Ratcliffe and two of the Glazers) would have to agree. I think it's either the first or second options, but not sure which.