Interpretation of "from...to" vs "until"

John will be in New York from Thursday to Saturday" tells us only that during the forthcoming period Thursday-Friday-Saturday John will be in NY. This is usually on the assumption that the speaker is referring to the shortest such period, and not to (for example) next Friday and a Sunday three weeks later. We understand it as a forthcoming period that has not yet started, because the speaker used the future “will be”. The statement tells us nothing about where John was, is or will be outside that period.

If we want to say this is the only time that he visits NY, we have to say so explicitly by writing more. “He will never been to NY until Thursday. He will be there Thursday to Saturday. He will never visit NY again.”

"John will be in New York until Saturday" tells us only that John will be in NY during a period that ends on Saturday. The statement does not tell us when that period started, or that he is there now - although it is often be used in that way. It tells us nothing about where he has been until now, or where he will be before the period starts. Nor does it say where he will be after Saturday, although it is often used to imply that he will leave, and hence not be there on the next day, Sunday.