I assume most games with quests were still Flash based games, which might explain why only two are currently available. See also Armor Games' statement on Flash here:
Bah, everyone has read this article, I wanted a date, when will other quests come out? the end of the flash was not supposed to be so radical, even because the internet explorer can activate it
Other quests will probably come out when AS3 games with quests become available which will be, as it says in Ruffle's FAQ, "in a few months". Yeah, nothing more specific than that, sadly.
I hope that at least some will be supported by June.
