As stated above, PDF is usually ready about 3 weeks after the KS, so mid-December. Physical books will take longer, of course. As for getting them now, go for it! Per Ikael in this very thread, "Backward compatibility is one of the most important design principal in SWADE including FG conversion I am working on". So there's official word from the FG-side to help ensure backwards-compatibility. Then again it shouldn't be a big issue even for stuff that isn't changed out in prior modules as you should still be able to use them largely as-is. Either using them as they are or doing minor tweaks as you play them. Most things won't need much in the way of changes beyond maybe substituting Athletics for some of the rolls it would replace or the like.