Just for some perspective, calibre itself has over 300,000 lines of code (estimated at 82 man years of effort
http://www.ohloh.net/p/calibre) and has been developed over six years.
And calibre is based on a relatively mature, stable and powerful platform - the personal computer. Making a "calibre for mobile" app given that mobile platforms are fragmented, underpowered, unstable and immature is not something that is likely to happen any time soon.
More likely what you will get will be frontends for calibre, like calibre companion or the calibre content server.