If you really think about it, the China visit is the only thing going “right” for Trump since his inauguration other than maybe the inconsequential steamrolling of Venezuela. Domestically he is facing insurrections in the MAGA faction that demands accountability for Epstein and Iran. Deep down even a narcissist like Trump is grateful for Xi’s magnanimous hospitality display.
I think this is right and as I said in the news thread, it has been noticed for a while now that US president can agree to stuff at an official meeting then their agreement doesn't actually get carried out by the state machinery afterwards, this is very annoying to CPC because they expect the words of a country's leader to be paramount.
So this time measures are put in place to avoid this. Rather than agree to conditions flat out China will now agree to things but only fulfil them in stages contingent on how US sticks to their side of the deal. Hence we see things like buying 200 Boeing but with the promise of further purchase up to 750 "if the conditions are right".
Xi agreeing to visit US in September would be another one of those staged approaches. If Trump cracks down on pro-independent voices in US and does something about the weapons sales to Taiwan then yeah sure, Xi will go in September and boost Trump for his midterm. That's why Trump is calling that a card and why he's saving it up to use later rather than talk about it right now.