So far no upgrade, but since it is still pre-release it is not outside the realm of possibility, but I doubt it will be available. IMHO you should always do a clean install anyhow rather than 'upgrade', in fact you'd be suprised how much faster your computer will seem after a fresh/clean install of Win-XYZ, particularly if it has been two years or so. I was in the habit of formatting and re-installing every year, but I tend to abuse my system
Anyhow, you can download XP-64 for free right now. I cannot get AH2 to work since my sound card is too old to have 64bit driver support with DirectX, it is a SBLive.