I'm getting ready to release the first early access version later today. (around 5 or 6 PST)
Be warned it will break some save game compatibility. If you are on chapter 2 or 3, it will reset your map, but you'll get to keep your party(levels, cars, weapons, inventory). It will not effect your profile or achievements in any way.
I've made a beta called "legacy" available that uses the old save game version. You can use this to finish up before switching to the new version.
And if you time the reset right, this might make certain achievements easier, like "Rock God" or "Scrapper" which are two of the best, and hardest unlocks in the game.
I don't think there will be future save game compatibility breaks. And if they do occur, I'd like to give you more notice, but this came up during a prerelease play test, and I'd rather break it now, rather then when the game is public.