Bitcoin Core 0.16.0 (final version) has been tagged so It should released in the upcoming days, I expect most exchange to implement SegWit (assuming that they were serious in the past when they said they are waiting for this release). A transaction with 1sat/byte (currently) can get confirmed after a few blocks only so as long as we have no spam attacks, we're good.
LN developers already warned about using it on the mainnet, yet people are still doing it. So, It may take sometime before we see it in action (I'd say the end of the year maybe). You can see the testing results here: https://cdecker.github.io/lightning-integration/ (see this video
https://vimeo.com/256250634 )