How about blog abandonment 😉 (ouch, cheap shot)
I can only take some wild swings, but must note that a measure of “widespread use” has a bit of a Horizon Report-ish trap there.
* Mobile as primary device access to the net (maybe more of trend), mobile-first development strategies
* Seeing the (mapped) world via Streetview
* Mobile network speeds on par with broadband
* HD movies on mobile device
* Animated GIFs as a response rather than a 90s throwback
* How can you leave out DS106?
May all your blog dreams come true in 2020 😉