While many conservatives lauded the decision because of their rejection of climate science, the Trump White House, officially, exited out of the deal because they believed the terms of the agreement were too restrictive on economic interests. It's possible that the Trump administration has loosened their demands, and if so, then that would signal a re-entry to the eyes of some diplomats.
Whether or not it actually happens is another thing. As I said earlier, his base wanted to exit the agreement for ideological reasons - not economical.