No, the reasonable model (as someone how's shipped commercial libraries and researched the market) is that subscription gates support and future updates. So as long as the subscription is active you get updates, patches and support. Once it passes you're kept on old version. It's fair to the seller (keeps a steady revenue stream and most customers will want to keep the subscription for updates anyway) and fair to the customer (they can't be easily extorted with price hikes and their software doesn't get sabotaged by external subscription pricing).