From AT, in my comments, came another interesting look at the project language numbers on sourceforge…

Using filters on SF.NET (it allow to select projects based on multiple criteria)

I've what:
Stage......   Java    C#      Java/C# Ratio
Planning...  3459    476    7,26
Pre-Alpha.. 2302    292    7,88
Alpha......    2090    237    8,88
Beta.......     2438    258    9,44
Production. 1803    146   12,34
Mature......  122      13     9,38
Inactive.....  93        8      11,62

It looks like C# projects is still under development. So not everything lost, once C# will go to production this will possibly result in second round of development.

These numbers show the growth of C# projects starting compared to the number of new Java projects. Older projects show a 12:1 Java:C# ratio, but the C# growth is strong with only a 7:1 Java:C# ratio for newer projects.  Again, not enough to draw conclusions, but another interesting look at the data.