According to another comment in this thread, Freenode has 90k CCU, with hundreds of thousands over a period of a few months. The best number I can find for gmail is here [0], which shows Gmail had 72 million active users on android 6 years ago. Sorry to say but Freenode shutting down wouldn't even be a blip compared to gmail shutting down
[0] https://www.nielsen.com/us/en/insights/article/2014/tops-of-...