As the PP said, Disney will transfer luggage from one resort to another if you are doing a split stay. There are a couple of things to be aware of (neither are deal-breakers for us, but something to be aware of):
1. The luggage will not be available at the new resort until after 3:00 pm
2. You will need to call bell services/be in the room to have it delivered (it's not like DME where they will drop it off even if you're out).