I guess I'll contribute my own rant . WebGL tooling is maturing pretty nicely with tools like PlayCanvas and GooCreate. The studio I just started working at built this with the latter. As a designer/art director I like tools like Hype, Stencyl, Goo Create, and Unity. It's a different paradigm, by putting equal emphasis on content creation and development. Certainly this is a balance that's hard to strike for any type of interactive toolset.
I do think timeline-based packages are more 'designer' friendly, because the actual content creation is much easier on a linear timeline. Adding interactivity by scripting timelines is an easy concept to understand, and tools like Hype make it even easier.
A separate WebGL package would be cool – but what about all the 2D UI? A lot of the awesome WebGL content is mixing 3d/2d, similar to the site I linked to earlier, or the Halo Guardians campaign for instance.
To @jonathan's point, the debate about code generation will persist. In the 'Flash-era' a designer, animator, and a developer might work together in the unified environment. This has changed a lot, and nothing really exists in the web space that's similar. Game engines do a much better job at building software for designers and developers. Aside from my personal projects, anything I do in Hype never gets to production. The TD's generally want to build something custom using greensock or whatever, and I understand that. There's still value in prototyping something real that you can mess with in the browser – a huge advantage over the After Effects motion comp route in my opinion.