IK is now to the point they could offer a subscription if they chose. How about it IK? If the price is right, you could be looking at steady monthly payments instead of lump sums and customers may warm up to it. It has worked for various other companies, it could very well possibly work for you. You never know if you never try.
People would still have the option to buy plug-ins from you. It is just you will have another option for those who may want to go the subscription route. Some people would warm up to paying less each month to use your plug-ins more than they would spending lump sums to buy the plug-ins. However some may not and they would still have the option to purchase if so chose. Win/win for you and the customers.