Twitter announced enhanced profile pages for brands in early December, and the official roll out may occur next month. BusinessInsider reported from a source that the enhanced profiles will roll out after February 1st.
There are a handful of companies who currently have enhanced profile pages including, Coca-Cola, Bing and Staples. The new pages will allow for custom header images, featured (or promoted content), and a more consistent mobile experience.
In addition to the confirmed features, BusinessInsider mentioned vague information about iFrame environments being added as well.
For more information see the official Twitter enhanced profiles page.
Postscript by Matt McGee: AdAge is reporting that the expansion of enhanced profiles will only be available to advertisers that are currently spending at least $25,000 on Twitter.