Yes, it amounts to a cancelling and rebooking, it might make it a bit more seamless if you call Disney (assuming you booked directly in the first place) and get them to do it, they might just be able to reduce the days on your initial booking without cancelling and then make a second room-only booking, if you want to keep Pop as your first hotel. Did you book tickets too? You'll only need to buy one set of tickets to cover both hotel says but make sure they start with your first booking! If you want the deluxe hotel to be your first hotel then this is going to be more complicated and you'll definitely have to cancel and make two new bookings, with the tickets attached to the first booking.
I enquired about this recently - there is nothing special about a split stay, it's literally two hotel bookings with the second being a room-only booking without tickets.
Another option for moving hotels is to give your luggage to bell services and ask them to transfer for you as mention above, but then just go to your park as usual in the day and go back to the second hotel at night instead. Or take a break late afternoon to go back to the new hotel to check-in and retrieve luggage.