The situation about the iPhone version is this. First, I'd like to stabilise the iPad version and make it as feature complete as possible. This means adding 2-column reading and Calibre support at least. I expect these to be out of the way by early January.
After that, I'll start working on the iPhone version. Whilst there is a lot of reusable stuff, Marvin has a completely custom UI so it isn't that straight forward. To answer your question, it will be some time in February or early March. I hope my answer isn't too disappointing.