No doubt, anything that gets folks out on their bikes is a good thing. I love vintage geared bikes, but have no issues with conversions whatsoever. If it is a rare, desireable bike, I'd prefer to see the owner keep it original. If the bike is not really collectible, and converting it would increase the riders pleasure, then go for it.
The SS/FG trend is supposedly slowing down if you ask your LBS. I have visited about 10 shops this year because I travel a lot for work and stop into any interesting shop I find. Most all of them say it is on the wane. It probably is because I seem to always catch trends on the way down, not up.
Doesn't matter to me. I'll continue to ride SS/FG until I can't ride no mo'.