You aren’t guaranteed to get in. The beta is only open to Early Access members “in good standing” with a body of work, and Media Molecule will want to know what you’re planning, when you hope to finish it and whether or not you’re willing to provide feedback.
This could still be a big deal even under those current limitations. If it leads to a widely available program, you may have an incentive to use Dreams even if gaming is the last thing on your mind. While you probably won’t base a whole business around console software like this, it could provide a new avenue for art that was previously too difficult (or just time-consuming) to make from scratch.