Wild, once they (hopefully) fix this, if your villagers don't reappear, you could use a copy of your files from before W07A, then you would overwrite just the nether folder files (DIM-1) from your later work. I assume you weren't keeping villagers in the nether. Hope this made sense.
Will there be/is there any way at all to fix this? I spent many hours refreshing trades/zombifying+curing the villagers in my trading hall and I'll be absolutely fuming if all my work was for nothing.
it should be fixed in the release version or later snapshot, assuming Mojang have been told about the issue on the bug tracker and they can fix it, this is why snapshots are released, for testing and bug reporting