As PP said, yes you can.
To update from the QSDP to the Deluxe would be approx. $62/night. For that you get 3 meals (either TS or CS) and 2 snacks per night. You will also get an appetizer at each sit down lunch or dinner (not inc. on std
DDP)
I would look at the meals you want to have and see if it will be worth it at $62/per night/per person. Eating 3 sit down meals will take up a lot of your time.
If you want to upgrade from QSDP to reg. DDP it would run you about $28/per night/per person. For that you will get 1 TS and 1CS per night vs. 2 CS meals. You'll get the same 1 snack and refillable mug.
If I was considering upgrading to this one, again, I would look at the meals I want to eat and see if it makes sense. For example, for the $28 you'll be gaining a TS choice but you can't just look at that cost-you need to deduct the cost of the CS meal you are giving up. Lets say you'll have a meal at your food court. Entree around $10, dessert around $4 and beverage around $3. Total average food court meal about $17. So if you add $17 and $28 it comes to $45. That would be the value of that added TS meal. Looking at character meals they run in the neighborhood of $31 for lunch and $43 for dinner. Breakfast character meals are less, around $23-$27.
I did not factor in tips as those are OOP no matter if you have a DDP or not.
As you can see upgrading a DDP is not an easy thing to answer. So many factors.
The Deluxe plan is very nice, just now that in order to maximize your value you will be spending a lot of time eating. You can have 3 TS meals a day. That would be a minimum of I would say 4-5 hours per day eating, not counting travel time and waiting.
My above numbers figure getting QSDP for free (value resorts) if you would be getting the standard DDP for free then the upgrade would be about $44/per person/per night.
