Right now to detect new subscribers in my bot it takes the “xxx just subscribed!” message that twitchnotify posts and extracts the username from that message.
However since Twitch are introducing $9.99 and $24.99 will I have to change my bot to ensure all new subscribers are detected?
The twitchnotify account will be deprecated when the new system rolls out (according to this post: Subscriptions Beta Changes)
So you will have to make sure the bot detects USERNOTICE event from IRC instead of the twitchnotify account, just like re-subs.