I think if they were to expand it and to rival Disney Springs, the expansion would have to hit all the areas Disney missed and one for such is an ice skating rink. You get those super hot summer days and people will want to go and do something that's rather chilly.
Add a free entry Universal Museum...It has been around since 1912 so the history of it is immense and so many stories could be told.
I think a stage venue would be great, the problem is getting the rights and making it exclusive to Universal. La Nouba is so popular at Disney because they have the only La Nouba show in the world and if you were going to do a musical, it would have to be top tier awesomesauce that the entire family would enjoy. Suggest two theaters each with a different broadway style show one geared towards women and the other a comedy and the show change out every 3 to 4 years.
Add in a dining in the dark restuarant, (the restaurant thats pitch black and you have to eat in darkness, a cool mobster based restaurant, a indie/hipster bar with local indie groups being booked to perform and poetry readings etc.
Add a huge bookstore. Some people like to have down time on their vacation and though the sales on digital books are increasing a lot of people still like to have hard copies.
Make a park like area with fountains and no shops but just nature and maybe so horse drawn buggies. When its all set and done sometimes people just want to enjoy nature after a long day of being in a park. Walking down a brick lane, late night with their SO or riding a horse drawn buggy just adds a little simpleness that is just nice.
Make a neighborhood like area filled with mom and pop specialty shows...like a mom and pop soda shop,an actual bakery, a barber shop, a drugstore along with one of a kind stores with exclusive Universal merchandise that everyone will want. Just because you are on vacation doesn't mean you won't use these shops.
And then if they still wanted to expand, I would mind a little Italy, Chinatown, Louisiana Bayou etc breakdown with international cuisine that could rival Epcot.