The only classic Universal attraction I can see them bringing back is Back to the Future, just because I think it's both timeless and very easy to convert into several types of attractions. Meanwhile, I don't expect Jaws to EVER come back in its own ride, and if E.T. ever leaves, he'll be gone for good.
You would have to have Michael J. Fox and Christopher Lloyd reprising their roles in the 2015 standards, then you would have to explain how 2015 turned out. Besides, BTTF is nothing without the two people, and it's an old franchise that isn't relevant in the movie industry nowadays anymore (unless there are talks about bringing it back).