Life is one big evolutionary process. Obviously, you are the best judge of that evolution, but if you are curious, here is how to know when you are truly ready to transition from wing surfing on your SUP and daggerboard to winging on a foil.
Ideally, you want to be able to wing comfortably back and forth on your SUP and stay upwind. The more wing control you have under your belt the better! Being able to run and jump with the wing on the beach, riding with the wing on a skateboard, skis, or ice skates will help build your wing control skills. Make sure you have proficient wing skills before attempting the foil.