Sorry I missed the original post, but VSTO is not replacing VBA, but
enhancing the VB,C# etc control over the Office objects. VBA and VSTO are
two separate beasts aimed at different audiences. The power user versus the
commercial developer.

VBA is in Office 2007 and will be in the version after that. Microsoft has
committed to announcing when the last version of VBA will be released.
Office 2007 is not it.