Yeah I can picture tons of people start to get into the genre, but then come here and get flamed for a stupid post which will then make them realize only complete turds play these games...
Honestly though, I can see the genre growing in the future partially due to iTunes, but also the console online marketplaces. Think about how many people have seen something like R-type for download and though "damn, I used to love that game - too bad they stopped making shooters though"...
Another thing I've considered: even though I'm not crazy about achievements, in alot of ways they are helping the cause. Gamers are now interested in mastering a game rather than just playing through once, and it makes them feel extra satisfaction by earning points (mmmm delicious points).
iShmups arn't going to single handedly revive the genre, but they are definitely going to open a lot of peoples eyes. And US Deathsmiles and a couple games on iPhone are hopefully only the beginning for Cave - and if anyone can light the path, it's them.