As from the roll-out date of the subscription-based licensing model for IDA Pro, any NEW license of IDA Pro will need to be purchased under a subscription-based licensing model, as per Hex-Rays new subscription plans.
Remaining under a perpetual licensing model will only be an option for existing licenses bought under the perpetual licensing model. However, Hex-Rays strongly advises customers under perpetual licensing terms to migrate to subscription-based licensing terms in order to benefit from all the forthcoming technology evolutions of IDA Pro.