I wonder if they will forbid ingesting legal cannabis for recreational use.
The latest elders' manual (12:15.4) specifically mentions "...a practice of abusing addictive drugs, including betel nut, marijuana, and tobacco" as a disfellowshipping level offense.
It then goes on to mention that an exception may be granted for cases where a "medical doctor authorizes and/or prescribes marijuana for a medical problem".
I can see a lucrative business opportunity for an unscrupulous MD to "authorize" the use of "medical marijuana" for JWs. Requests from kids of wealthy elders alone would be enough to allow him to buy a 50 meter yacht and dock it in Monaco.