Yesterday, at EclipseCon there was a BOF called "Mega Modeling Mania", which was pretty interesting. It started with a discussion whether UML is a good starting point for domain specific languages or not. Some people argued that with profiles you can do a lot of cool stuff, but the tools have failed. But in the end I think (and hope ;-)) most people were convinced that there is no point in starting with such a huge meta model with hundreds of concepts in it just to design a language having couple of them.
After that we were discussing whether Ecore is good enough for meta modeling. Some people would like to see CMOF concepts like "Package Merge" or "Associations". Actually, the absence of associations was one of things I really liked when I started to do meta modeling in Ecore. And until today I never missed them. I got the impression that it is more a matter of taste, and that people who meta model using graphical syntax and often use bidirectional relationships want to design them at once. So to me this sounds more like a tooling thing...
Package merge seems to be an application of model-to-model transformations. And because it's so specific it makes sense to have a DSL to describe those transformations. Markus did this when he developed XWeave. Actually Achim Demelt told me that XWeave is even more powerful than Package Merge. So why should we want to have that in the core, i.e. EMF? It's already there and you can use it if you want.
To me everything seemed unecessary complicated.