Somehow I get the feeling that EK will not announce the 4th tier until concourse 3 becomes operational and their newer (and larger) lounge facilities come online. Assume for a minute that the 4th tier will give F lounge access irrespective of class of travel. I doubt they want to crowd the existing F lounge with 4th tier folks - they'd ideally want to get the infrastructure set up first and then deliver on it. Otherwise, the levels of satisfaction will run fairly low in the 4th tier and people will begin to question why did they introduce a higher tier if they couldn't deliver superior benefits.

Again, this is just an opinion....