For some days ago Misha Sheerson published an article about using the present version of the COM Shim Wizard for the coming Excel 2010 64-bit. This is an iterim solution and we should expect a new updated version of the COM Shim Wizard when Excel 2010 has been launched.
I must admit that I have been worried about what will actually happen, especially if we consider MSFT strong commitment and focus on VSTO. It’s good to see that MSFT has not forget the group of developers that still create custom solutions based on the Shared Add-in in Visual Studio.
For more information please see: Taking COM Shim Wizard to 64-bit