There is no set date on 2.1, as you can see here:
There is many, many "active" tickets still open.. 2.1 is for testing purposes only..and the more people to help squash those 200 and some "bugs", "active/open" tickets..the better.. =)
2.0.4 is the latest version now. *Only* grab 2.1 alpha2 if you're going to help test it, and squash bugs.. ;) Also, 2.1 alpha2, *should not* be used on a "live" blog/site, even though..*some* people do it, however..those people know what they are doing with it though... ;)
And an upgrade will be need for the 2.0.4 to 2.1, there was a number of database changes, if I remember right.. path changes for files/folders and so forth..