The latest passenger & freight versions are the -8I & -8F respectively. They were first delivered in 2011 & both have been slow sellers since Day 1. The 8I- hasn’t been ordered by anyone since 2016 and the -8F since 2018.
If nobody wants to buy them there’s not much reason to make them.
Back in 2018 they’d already slowed production to the point that due to overhead they haven’t made a profit on the last few units built nor will they make a profit on their few remaining unbuilt orders. The earliest parts for any given airplane need to be ordered from the most upstream suppliers about 2 years before that airplane will fly. Said another way, once the pipeline of unbuilt orders is shorter than about 2 years you’re about to start buying parts for planes you haven’t sold. Once you decide you won’t be able to sell them there’s not much reason to order those parts. And that signals the end of life.
The 747 has had a good long run; there’s nothing inherently embarrassing about it finally getting to the end of its natural life. But with all the other negative news about Boeing, there’s always an executive desire to keep some happy prestige thing looking healthy. The industry has been watching Boeing sidle up to pulling the trigger on this for at least a year now. It’s all still rumor today, but the betting is it’s real soon.
As folks just upthread have said, the existing airplanes will be flying for 20+ years to come. The existing passenger versions will probably be converted to freighters sooner rather than later.
OTOH, if nothing else, any business that was looking at an embarrassing decision of retrenchment now has a really handy excuse in COVID.
“COVID made me do it” can excuse a lot of executive goofs. Whether those goofs are smart people who predicted wrong, or dumb people doing dumb things. Or even criminal people doing criminal things. COVID makes a great cover story for all.