I'm not defending ED but this has been beat to death so much I'll just repeat what's already been stated by them.
The reason that ED continues to work on 1.5 is because of the free Caucuses map.
It's been speculated that 2.0 is really just what 2.5 will be once the Caucuses map is upgraded.
So 2.5 will just be the new Caucuses map rolled into the current 2.0 along with NTTR and other payware maps.
Development has to continue on 1.5 because the 3rd party developers and ED support all of the modules in that World with the free map.
And there are still a lot of people out there that haven't or won't pay for NTTR and only use the free map.
They have stated that the Caucuses map will still be free even though it's being turned into a high resolution version.