There will definitely be carts in addition to the tavern.
Personally I think we'll still have The Three Broomsticks, just a much smaller version that'll have less food options on the menu compared to Florida, and focus more on the speciality drinks. The tavern is very iconic to the movies and books.
Regarding a bigger Hogwarts, it makes me giggle and roll my eyes when people say we'll get an exact scale Hogwarts at USH all the time....Hogwarts is bigger than the entirety of USH, CityWalk, and almost half of the Backlot
Also, the forced perspective scale of the Hogwarts structure is already great. Bigger would be cooler but it isn't a necessity. All that other extra stuff that would be "inside" would just mean a bigger show building or a few attached show buildings. That wouldn't and shouldnt affect the rocky cliff facade or the scale of the Hogwarts castle structures.
The Defense Against the Dark Arts/dueling wizards show and Great Hall restaurant were all rumored (or planned) parts of the original Wizarding World when it was being built. I remember many people were excited when these projects were brought up and then sad when it didn't actually happen. So maybe we're getting the scrapped projects that were originally planned for Florida's Phase 1 to make up for not having Dragon Challenge.
I think a Great Hall restaurant would be one of the hottest and most popular restaurants in all of California.....especially if it would have the rumored CityWalk Great Hall entrance as well!
Also, ScreamScape also posted this:
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"Oh… and for the record, don’t think that they are done with the Wizarding World once this phase opens in 2016. While obviously nothing will be decided and made official for years to come, there is a loose plan to possible create an expansion. Since land space is a major issue at the Hollywood park, they may take a nod from what is being built at Orlando right now, and look into building a Hogwarts Express ride that guests can ride out into a section of the backlot where another Diagon Alley would be built, complete with a copy of the Gringott’s Bank coaster ride. Don’t look for Phase 2 to happen until at least 2020 however… and only if the Harry Potter money machine is still alive and well for them by then."
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I personally still think that'll never happen. I can't see us getting a Hogwarts express taking us to a Phase 2 over the hill somewhere on the backlot. I want Orlando to keep something original. And I don't want our tiny park to be 50% Harry Potter....