I'd really love to see the combination of all the good things of social media coming together.

Groups with voting like Reddit. Sub groups like Discord. Friend feeds like old Facebook. IM like Discord. A disappearing posts feature like Instagram/Snapchat. Events and things to do in certain areas like S'More. A revamped phpBB forum style in groups. Etc.

And good monetization practices, e.g. selling ad space on groups or on keyword searches.