Interesting, as the USB150 was just on Black Friday sales and is still available on Amazon. It is my go to router when I’m out and about, as it fits in my laptop sleeve. Also @alzhao stated there would be fixes for the GUI in 4.x for the USB150 in this post.
Usb150 updated to 3.105 luci is not working well - #12 by alzhao
So per your reply @alzhao only knows which products are going EOL and how long they will be supported. Since some new products like the Brume-W are already going EOL where some of there older products are still fully sold and supported, any statement made by anyone other then @alzhao on product EOL is just a wild guess and should carry no weight in making a buying decision.