The road leading out is the proposed second gate. Its currently used for events and bus parking. Universal is too meticulous about their theming, flow, and "every guest gets the same experience" to do a second gate. And let's talk about the most of the guests: Overall, a majority of the guests would still go through PoE, but let's look at onsite hotel guests... the CBB is 1800 rooms, that's the size of the Royal Pacific, the Portofino Bay, and 50 of Hard Rock's rooms combined. During the summer, that's a large chunk of guests who are going to skip City Walk altogether.
What people keep forgetting is that IoA is not the sum of UO. That'd leave access to USF and City Walk to be determined as well. The only access they'll do is somehow to City Walk. Exactly what they'll do is open to the imagination.