If you're a huge fan of Castaways and just can't wait for the next update then look no further. You can play a new development pre-release every week. These pre-releases are experimental. They contain features that aren't fully developed yet, and some may be changed or removed.
Please note that the pre-release game takes place on different servers than the official release. So your account, world, and inventory will be different and cannot be transferred between versions.
You can see what's changed by reading the changelog.