The New Yorker […] demanded not only design fidelity, but flexibility due to its weekly, text-heavy nature. To solve this design and production challenge, The New Yorker used HTML pages as part of its tablet edition. HTML provided flexibility for The New Yorker to rapidly flow text into the magazine application and meet the requirements of a frequent publishing cycle. In the future, the Digital Magazine Solution will provide the option of using either HTML pages for flexible publishing or rasterized images for publishers that demand pixel-perfect layouts.
My translation: Yes, the team is well aware of file size concerns, and they’re using various technologies (e.g. HTML) to give publishers choices. I expect we’ll be hearing more details soon.