I’d move on.
If the start-up has a term sheet, a real offer from an acquirer — that’s one thing. I’d wait a week and listen and hear what it is. Sometimes (though not usually), the retention packages for non-founders and non-VPs can be attractive. And your equity in the start-up may (or may not) be worth a lot more if you stay though the acquisition.
But …
“get sold in the coming months” often is a pipedream. If there’s no real offer on hand, or something at least very close … odds are, it ain’t real.
