Looks good!
What material are you looking at making these out of?
If you're thinking aluminum -- I suspect the hub in the center is over-designed.
If you're thinking plastic -- I suspect the "spokes" are under-designed.
You can also probably get away with only (3) sprocket attachment holes.
You should consider some form of piloting feature to keep the sprocket concentric with the wheel (or cheat, and use the bearing to pilot the sprocket).
Why did you decide to go 4"+tread? I think you should consider making the wheel 4" at the OD of the tread. This way if you have robot turning issues, or need to swap in some COTS omni-wheels or other traction wheels in a few places you'll have options. (This has 100% happened to me in the past... being able to swap wheels around has saved my butt several times).
Keep going. You've got plenty of time for more iterations before you need to make these for realsies.
