according to the stats page
BotB has been growing slowly but steadily for over a decade, picking up the pace over the last few years especially. the site is however yet to have what might be called a 'viral moment' - the growth isn't punctuated with any sudden spike in interest or burst of new users, just gradual accretion.
i think it's inevitable that, sooner or later, some BotBr or other is going to be involved in some project which goes mainstream (probably an indie game OST) and fans interested in digging up more of their work will find BotB en masse.
i wonder how the community will handle the flood of new members (most of whom will likely have no connection to or interest in the chiptune/demoscene subculture). it will be BotB's great acid test.
i wouldn't dare try & predict a deadline for a black swan event like that. might as well speculate on dogecoin.