Nobody mentioning EVC? Worth a read for anyone concerned about patent licensing:

https://en.wikipedia.org/wiki/Essential_Video_Coding

There are 3 video coding formats expected out of (former) MPEG this year:

https://www.streamingmedia.com/Articles/Editorial/Featured-A...

So this isn't necessarily the successor to HEVC (except that it is, in terms of development and licensing methods).