It is a bait and switch, because he will still be still maintaining the software, but under a proprietary license. If he stopped maintaining it altogether (as in your "imagine" examples), then you'd be right that it wouldn't be a bait and switch.
What’s the switch? You have everything he’s done up to this point as FOSS. You could continue to develop it yourself, if you wanted. If you were using the software expecting free updates into perpetuity… that’s on you.
