Hi there -
Yes - you would be best positioned to migrate to the NAC Appliances for best support of future versions.
Changes to the way that customer supplied hardware is supported could happen as early as 4.5, which releases later this summer or early fall.
Please ask your account team to contact me and I will provide them with additional details they can share with you directly.
I hope this helps. Let me know if you have other questions.
thxs
peter