I am primarily interested in the interplay between standards like EPUB3 that are based on the web platform, and the base capabilities of the web platform itself. Aligning EPUB3 with HTML5 and CSS3 is a good first step. But that step needs to be followed by encouraging work-in-progress features (hyphenation, speech, etc.) along their standards tracks and pushing appropriate pieces of EPUB-specific markup and styling to become part of the general web platform. The EPUB3 specifications call out the risks in using work-in-progress CSS features. The IDPF should mitigate those risks by engaging more with the CSS Working Group on issues that matter to ebooks.
The more ebook formats like EPUB diverge from the general web platform, the more barriers are put up on developing readers and author tooling for ebooks. The more ebook formats converge with the web platform in general, the more ebook production can benefit from economies of scale in web tools and viewers. Reducing the delta between EPUB and the web platform (mostly through improving the web platform) should be crucial for the ebook cause. The goal should be to allow ebook production to use general web platform tools. The current tiny cul-de-sac of EPUB3 tooling is hampering ebook efforts, and time directed at filling out this tool chain might be better spent finding ways to make EPUB development more like web development (and vice-versa).
The general web platform will benefit from being raised to ebook standards. The adaptive layout needs of ebooks should inform the development of adaptive layout systems in CSS. Declarative pagination systems in CSS are being discussed (and prototyped in browsers) with very little input from ebook use cases. I am much less familiar with EPUB packaging, but offline app packaging is also a current topic and I naively expect there should be some convergence between the two. I am working on CSS features originally pulled from EPUB Adaptive Layout, and it would be useful to know whether the current state of these features still tracks EPUB requirements.
So my desire is for more and better collaboration between standards bodies that control the pieces that contribute to ebook formats. Let's minimize divergence and maximize the leverage EPUB gains from the general web platform.