You could always email them and say you lost your entire collection. I did that when they changed from small movie files to larger ones and they let me re-download everything.
Well, technically they are different files, so they don't *have* to update them for you. Just like you wouldn't get an update for your Mac just because they come with more RAM and a faster CPU now.
I would think they wouldn't let you get the DRM-free version for free. When we paid $0.99 for a track, we knew it had DRM. It will still continue to work as advertised. It would be nice if they offered the non-DRM for free, but I would expect some price or no option at all