Subscription model (or SAAS - Software as a service) now is a inductry standart in fact. and it's become a common delivery model for many business applications. Yes, it's a bit new for game dev, but not because it doesn't work, but because developers prefer add one digit to software version and sell Software++.
SaaS better for customer, mainly because all important updates implemented immediately, and developers not need to wait for next number relise.
It's also good for developers because it's more stable profit model.
I don't see any problem with subscription. 99$/y is a low cost for good game dev software.