Why would they do that? Linux desktop has no penetration into the market. It would be a big investment to capture an additional 1% market share.
I can see MS porting all their server apps(MSSQL, Exchange, etc) to run on linux since Linux is dominating the server market and it would be a significant opportunity for them.
I can see MS porting all their server apps(MSSQL, Exchange, etc) to run on linux since Linux is dominating the server market and it would be a significant opportunity for them.