How necessary is porting it, and for how long will old DirectX versions continue to work? Having no knowledge of the code, I imagine if you have a functioning

How necessary is porting it, and for how long will old DirectX versions continue to work? Having no knowledge of the code, I imagine if you have a functioning graphics layer, most of the work would happen on the underlying physics models and high level drawing/scene APIs, not directly interfacing with DX.