I don't think they are serious about this. It's a distraction from BIP-110 as it was gaining momentum. BIP-361, if I understand correctly, will have to be a hard fork as it sets up a precedent for which you can make certain BTC unusable based on which wallet they are stored in and how often they are accessed. That's just insane. It's FIAT mentality at its best. Nothing to do with BTC.