I am going to be frank, even tho it means I am also going to be bitter and depressive, and potentially even odious.
Dude, relax. You sound far from any of that!
I don't care if the hobby is shrinking (but I don't believe it is, or at least not dramatically).
All I care is if my gaming hobby is shrinking, but I can assure it that it has in fact shrunk to zero (posting on ENW doesn't count), but that's not because of WotC, D&D or the gaming community, that was just because many of us who played together reached the life stage of mating and multiplication, and we just didn't have nearly the same amount of time and energy to regularly play anything.
That has happened to most of my friends too. Heck, I don't think I know anyone my age who has as much time to play today, as he/she had 15 years ago. Life does get in the say much too often.
Now after a few years of retirement, children are getting more manageable and we're once again thinking of gaming, but my intention is the same as it has always been: to play with some of the friends I played before + adding more from my entourage of friends (old and new). I've always preferred converting my friends to players rather than converting players to friends. But I don't expect them to become geeks of RPG and start collecting books, I'm just fine that they play with us, and actually I prefer them to remain casual players since this means that as a DM I will have less problems (e.g. less rules lawyers and powergamers).
OK, what you're doing, converting friends into gamers, is indeed promoting the game. Specially because they might have children and might decide to start playing with them.
Or maybe they'll talk to other people about it and spark another flame somewhere else.
Or maybe your kids will enjoy it so much that they'll want to have their friends around to play...
Anything and everything counts. I don't mean for people to give up on anything and start a blog, or start writing adventures, or running groups when they have no time.
It sounds like people in this forum are taking to heart and assuming I am suggesting a massive effort and I'm not. The likelihood is that if you're in a forum like this, you're already doing your bit.
Would a bit more help? Sure! But I'm not asking for anything out of the ordinary here.