Mashiach Agent: I would imagine that the org would be oh so grateful but wouldn’t stop fundraising.
If this donor passes on and has descendants, chances are the donations will be much less if they continue at all. If there are no descendants, then the well will dry sooner or later.
What if the market shifts and this wealthy donor loses all or most of his money?
What if the yeshiva needs a new building? As much as someone may give, there is a limit to what they’ll pay for.