The only way a second gate would work, is if it took War of The Worlds, Whoville, Psycho, Falls Lake, and Supercharged, along with various backstage around that and the hillside. But even then, you'd have to deal with neighbors, relocation of the recently expanded warehouse, and re-routing vehicle traffic (not even mentioning the Tram into that).
However, with the seeming possibility of Potter expanding to the current tram load, it may be interesting to wonder where they could relocate that isn't the Lower Lot, as the only area that would come to mind is the original stop-area next to the Picture Cars and Collapsing Bridge.
I'm under the current belief that if Universal ever expands in California, it will be up north of California, like San Francisco north. But even then, that'd bring some worms in a few ways.