MERGED: Will the current version saves carry over to 1.0?

No. There will definitely be enough core changes that your A21 game won't be compatible with 1.0. If you think you might enjoy the game to play it through twice you could start now and ignore the experimental version when it releases and wait for the stable version while playing A21. That would give you at least a month's time to explore the game as it is now and then restart once the stable 1.0 comes out at the end of June.

If restarting and playing it through more than once doesn't sound appealing then you might want to shelve it until experimental drops in a few weeks. Experimental will be compatible with stable.