Do you mean you pack your luggage and YOU have to transport it to the new resort? We never have a car so this would be a problem.
Well, yeah, you have to pack up your bags yourselves!!! But Disney will move them for you. I do split stays all the time. In fact, my dd is headed to BWV for her high school graduation trip next month..with two friends. And she told me that she is thrilled to be staying in one place for the first time in years..no moving to another resort!!! Poor baby!!
So, this is how it works. Book your two stays. I recommend staying at the more upscale resort last. Then, on your last morning at your first resort, pack up and call Bell Services. They will come to your room, tag your bags and get them to the next resort. I tend to do this very early...about 7am-ish. IF there is anything you will need for your day, before 5pm-ish, take it in a smaller bag that you can bring to the parks with you. You won't have access to your other bags until late afternoon!!!
Then, I head to a park for a few hours..usually leave around lunchtime. I then head to the 'new' resort. I get checked in, and if my room isn't ready yet, I can head off to lunch...or another park.
When I return later that day, my bags are ready to be called for. They will not take them directly to your room though. You will have to call to have them delivered.
Or, you can just take a cab over to the new resort, with your bags, and leave the bags with Bell Services. At least that way you'll have access to the bags during the day..which is especially nice if your room is ready early.