Since in the 1980s in addition to retail and digital sales the business models we've seen have included:
* Pay-to-play arcade games * Premium hint lines * Add-on content sales * In-game sponsorship (Zool, sports games) * Shareware * Advertorial games (McDonalds Land) * Subscription fees * Peripheral sales * Real money betting * UGC Rev shares * Membership clubs * Game rental * In game ads * IAP * Virtual items
Since in the 1980s in addition to retail and digital sales the business models we've seen have included:
IAP is likely here to stay, but just like the many many business models that have existed before, it'll likely become one of many in use.