They've confirmed that they will be building extensions for other browsers and expanding BAT beyond the Brave browser. The Brave browser is, of course, the first proving ground and lets them implement the full platform without API limitations, but they've confirmed that insofar as the extension APIs are supportive, they will make extensions.

(And you can still make extensions that offer partial functionality, such as the a BAT wallet for donations, but without the whole BAT Ads platform built in. You would get full functionality in apps that integrate BAT with the SDKs or if you use Brave itself.)

They're also offering SDKs for other apps: e.g., mobile apps, smart TV apps, etc.

See this post: https://basicattentiontoken.org/driving-user-adoption-and-ex...