Just to expand on what Phil said, as long as Microsoft supports the 32-bit technologies used by your application then it should function. Windows 7 is more of an upgrade to Vista so I don't expect that you will experience problems in that environment that are any different than those in Vista.
Microsoft will be supporting the core run-time for a number of years yet. But that doesn't mean that extensions to your application will be supported (if you are using any). Beyond that it's rather difficult to make any predictions with respect to future versions of Windows.
Microsoft MVP (Visual Basic)