Absent mass mind uploading, I doubt that food in some relatively recognizable form will ever die out, or that we will ever find it economically feasible to eat food known to be made from human waste.
Fecal implants do seem to have some health benefits.
There are people who do drink their own urine. Spirilina can be grown on urine.
Algae also have the advantage that they are signal cell organism with means that it's easy to introduce new genes into them via DIY-bio efforts.
That means you can easily change the way the stuff tastes and let it produce vitamins and other substances. If you want a cheap source of THC you can transplant the relevant genes needed to produce the THC into an algae and grow it at home in a way that isn't as easily discovered as growing hemp.
You can trade different algae species and get more interesting compounds than THC.
What are fecal implents?
Few people do, and I doubt that it will catch on; spirulina can also be grown on runoff fertilizer, which will probably sound more appealing to most people.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.