To make tablet publications lighter weight & more dynamic (offering liquid layout, etc.), publishers need HTML to get smarter. Otherwise, to get the layout richness their brands require, they’re stuck with things like creating huge piles of PNGs.
That’s why Adobe’s been helping advance proposals for CSS Regions & Exclusions. To hear about the progress they’re making, check out CSS Regions: One Year In. (For background, see the demo below from a couple of months back.)