That way you can keep the players. Also, you will benefit from this and you can build the new game with DLC engine.
The experience with that upgrade will help you to design the next game and make it ready for DLC, without rebuild it after finishing
I just suggested something simmilar in the other thread:
There's also one potential bonus for David, in case he decides on making game editor. He could include user content he finds good enough in official EK versions, so EK could still grow after 1.2 relatively easy, leaving David free to develop new game and in same time, spending much less of his precious time, developing EK's new versions with user created content he officially approves.
In a way it would be a big plus for everyone.
Of course, we will see what will come out of it. I guess that many users who would create content wouldn't mind if it becomes officially included (of course, permissions should be given explicitly, but we could have special thread, or maybe even new forum for user created content, if editor becomes reality).
I know that it would take time to make game editor and make it ready for public, but potential benefit could be enormous. For example, each month David could use two or three days to cull best new content and include it in next EK version.
In this way EK will still gets updates, David time to develop new project and all in all, everyone will be happy.