Do you want to do Universal? Wizarding World of Harry Potter is an absolute must do as far as I'm concerned, and I think Universal Islands of Adventure is a must do anyway, even before Harry Potter, and the Spiderman ride has just had a major update to graphics. Spiderman was still one of my favourites last time I went, even though it was looking a bit fuzzy. It's amazing with updates for technology how what is amazing at the turn of the century becomes fuzzy over the years.
I generally say for DisneyWorld you need one day for each park, and 2 more days for return visits, you need a rest day in there, and a day to check out the lobbies of all the resorts. I'm amazed at how many people don't bother to go for a walk on the Boardwalk area, most of it is food based, but still a lovely evening stroll. You need a day for outlet shopping. Downtown Disney can be included any day you feel up to it in the evening. So that is 9 days without Universal or anything else Orlando has to offer, with only one day outside of Disney (outlet shopping), though only 6 park days. If you have a Magic Your Way package of room and daily park tickets (which you need for free dining), you can do shorter days in the parks and won't need a total rest day, just a partial rest day. And that doesn't include any water parks!
Before WWOHP you could do both Universal parks in one day if you just went hard, but now you do need to allow a second day for both Universal parks, plus it means you can go back to WWOHP. Even if you aren't a Harry Potter fan, WWOHP is a must see.
I like Sea World on the Gold Coast more than the Orlando one.
Then there is Busch Gardens, Legoland, Kennedy Space Center (you get to go through Melbourne and send postcards back to anyone in Melbourne Victoria you know
) , the water parks, Discovery Cove, etc etc let alone any of the day trip distance local area (St Petersburg/Tampa, Daytona, St Augustine, etc)