According to Googler Erik Tseng, Flan is out and Froyo is in. Froyo, of course, is short for frozen yogurt. It follows the alphabetical naming scheme perfectly, and I find it's a much nicer name than Flan. (It tastes better, too.)
One thing to keep in mind. Though Android 2.1 is already available on the Nexus One, it is still considered to be part of the Eclair branch of Android. Whatever numerical designation Froyo corresponds with was not revealed by Tseng. It could be anything.
We also have to start guessing what Google will pick next. It has to start with a "G". Thoughts? AndroidAuthority.com suggested ginger, gelatin, gelato, and ganache. I ain't got nothin' beyond that.