xingcat
Be good to self.
Considering the fickle nature of the internet, the ever-creeping takeover by big studios of places like YouTube (trending videos and highly-viewed/shared videos are most often promotional materials for TV shows or movies) and what may happen with different platforms that may push into YouTube's space, I don't think there are any guarantees at all. The next big YouTuber may be someone that nobody sees coming, who starts a format that nobody expected. Also, YouTube may introduce some new features we haven't considered that would make some other style of video a lot more popular. It's still a really new format, so I wouldn't hang all your predictions on gaming or any other type of videos at all.