I wish I shared your optimism, poivron.
Doing it for your health is a great reason, and perfectly rational. But I think it requires a deeper level of motivation than rational thought can provide. From what I gather people fail at weight loss diets almost 100% of the time, not to mention more acute situations like heart attack patients who continue to eat salty, high cholesterol foods etc. Abstract, hypothetical, long term health concerns just aren't enough IMO...even "ethics", in the academic sense, aren't enough...I think you really have to trigger emotions to reach someone on a deep enough level. Generally speaking, of course.
The health aspect is definitely helpful, especially after you've broken the habit of eating meat and cheese and your taste buds have adjusted and the consume/reward loop loses its power over you.
If this synthetic meat crap catches on - which it very well might in that 20 year timespan you referenced - the health argument will be a lot more important. It's harder to feel emotional about petri dish meat, even if those stem cells came from exploited animals.