The best way at the moment - as said above - is to download the version the demos were recorded in. It would be kind of cool, if a future version of Soldat, had the ability to revert (in a way) to an older version automatically - so that all demos could be played, but, afaik, even though possible, would probably be a major headache to code and certain things in the engine would have to be restructured - is my guess. So, most likely that won't happen.
What would be nice to see, now that I think of it, is a program that could detect what version of Soldat a demo belongs to (dunno if one exists). I have a small collection of demos that I've found over the years. I can usually tell by the file date, but sometimes I get odd dates or the version that corresponds with the date can't play the darn demo (even if all necessary maps and whatever else exist).
