Seems like the interest to work on sidechains has died in favor of Lightning and Segwit ( I might be wrong about this, that just seems to be the vibe I get from social media and seeing what kind of things people are working on and excited about). There doesn't seem to be much interest in the required soft fork to get side chains working ( See also this question where it was predicted that this would be done in 2016, well now its 2018: Is it likely that side-chain support will be added to Bitcoin? ).
Some Core developers like Peter Todd have also expressed serious concerns about the potential downsides ( https://soundcloud.com/mindtomatter/ltb-e104-tree-chains-with ). There also seems to be political obstacles to enabling side chains because it is not clear what benefit it would give to Bitcoin itself.
So what kind of progress/work is being done on sidechains and will sidechains ever see the light of day?