The new Blogger Beta has been around for quite some time, yet the option to switch to the Blogger beta is being offered to a limited few blogspot users. Even my earlier Blogger account has still not been offered the upgrade.
They mention some factors which may be causing the delay like –
* A blog publishing via FTP to a non-BlogSpot server.
* A blog with a Plus upgrade (we stopped offering this upgrade a couple years ago, so this will not affect many people).
* A team blog.
* A very large blog. (More than a couple thousand posts + comments.)
If you dont fit into those categories, then I guess the known issues and outages are delaying full public release (that is why it is beta!).
But if you want to try Blogger beta now, create a new beta.blogger.com account and they say you’ll be able to merge this account with your original Blogger account later. Remember the new Blogger requires login with your Google Account username and password (though the login form is still on Blogger.com).