In my opinion, a debugger/profiler should come far before multiplayer or any complex feature like that. It helps already made projects and the ones to come, especially when mobiles are the targets.
Modularity sounds nice but since it's a more abstract feature i think more explicit features could be made faster or more easily.
Sounds like it could have it's own poll. Or could be added in mini updates.
The most needed feature, along a debugger/profiler to me, it's a more focused atention into microtransactions on the most popular platforms (iso/android/windows phone). Similar to the level reached with windows 8.
I think that close the circle better for us as developers.
Then, with a foundation that works good enough at development times and also at release times you could add more features like multiplayer and the like.
Well, that's my two cents (I never liked that expresion ;) )