IE 10 touch and iOS won't work with Flash anyway, so I would hope social game developers are at least looking at HTML5 for their next projects.
I sometimes wonder why their isn't a cross platform "game browser"? It seems one of the cross platform game engines could do a much better job than flash. Adoption is a problem, but people seem to be able to download a lot of apps these days.
A big reason that Flash still wins for game development is that audio support sucks in HTML5 and silent games are no fun. An example - Mobile Safari only lets you play sound on one channel.
I'll take that as a given, but that isn't the whole story anymore. A PS/3 has better performance than Flash, but it is harder to program for, harder to distribute on, and has a much smaller market share. Flash has been losing market share for a while, and now the cost of distribution is going to be an issue. The likely successor is HTML5 (at least for browser market share). It is not as performant and the tools are not as good, but its what we got unless someone does something interesting and radical.
Flash isn't harder to program for or distribute on. It's so easy to build in kids make games, and it's so easy to distribute since they're a single self-contained file that those kids can make games that get country-sized volumes of traffic playing them.
You cannot possibly put HTML5, mostly three.js at this time (thank you Mr Doob, you rock Sir), at the same level as what Flash is able to do on a browser or what Flex is able to do on mobile. It is also not supported in some present browsers. Neither targets "social gaming" at all. Adobe is doing HD specs at 60 fps, full GPU render support. What other cross plat does this in the browser at this point and what other cross plat that does this aims at social game developers even? HTML 5 does a better job at what ? 8 bit looking socket based casual games and full 3D are not the same thing. IE 10 is lining up to miss on browser level AAA looking games and iOS prefers to determine the "future" where it is able to vote, none of this brings hardcore gamers in no matter how anyone may want to present it. Look at the triple A titles that sell, look at what Abode is doing, then look at what three.js does, does it look like social gaming to you ? Let's be realistic and not just play along to a party line. In the process lets also not build up casual gaming to be something that it is not, some sort of made up standard for what gaming should be just because it is of interest to push for specific tech at a specific point in time. It is getting old already.
I actually do not think HTML5 is a replacement for Flash (thus my second paragraph). Regardless of the utility and capability of Flash, it is no longer a universal platform. Since it is losing market share (browser with flash / browsers without), I would assume people in the social gaming area are starting to look at other platforms with HTML5 having the largest market share.
"...it is no longer a universal platform."
Was it ever ?
Media diffusion is not something anyone should disregard depending on brand. Present penetration numbers are still impressive unless you have other data. That creates a blind spot in the rear view mirror for someone wanting to isolate social gaming in a area where only one technology is enough, sometimes even the only one that is "acceptable".
Let us see how people like Mr Doob push javascript and the progress that comes in adopting easier render pipelines, it is promissing at this point. maybe everyone is going to want to have the next V8. Maybe webkit, html5 and canvas3D are going to have to get along in the end because social gaming is not part of a area but it exists in a place with some irregular border lines. Maybe some big engine comes and saves the day.
You do post from Unity to Flash now and starting a game with Flash and making the Unity plugin a must download for the rest of the game is the sort of thing that Adobe wants to secure a profit in. Unity posts to Flash. Sure, why not. Unity is a great tool but Flash is better at end file size, user penetration and web site integration.
I sometimes wonder why their isn't a cross platform "game browser"? It seems one of the cross platform game engines could do a much better job than flash. Adoption is a problem, but people seem to be able to download a lot of apps these days.