I'll take a crack at it......
The number of JWs will have peaked at around 8 - 8.5 million, and will just be starting to hold steady prior to a gradual decline.
There will be far more hours preached, maybe even 2 billion per year, but the number of baptisms will continue to drop.
There will be a serious shortage of elders and ministerial servants; in many congregations, just 2 or 3 of each.
Messages touting the "privilege" of donating funds will be more frequent and urgent.
Virtually all literature for JW consumption will be produced online; any printing will be done on the local level, of PDF (or whatever the standard is then) files.
Field service will be focused on leaving tracts and brochures; Awake will be exclusively online, and the "public edition" Watchtower will be mostly online with maybe 16 pages printed quarterly.
Field service will be increasingly difficult, as there is increased public awareness of pedophilia scandals & lawsuits. JWs will be instructed to "shake the dust off their feet" rather than engage in conversations about the topic.
The online "study edition" Watchtower will spend even more pages (if you can imagine that) trying to micromanage believers' lives. Advances in technology will raise all sorts of issues (e.g., is sex with a robot "porneia"?) that will be discussed in mind-numbing detail.
Virtually no kids will remain beyond the age of 18-22. The few who do will be the "superstars", and the males will be appointed as elders younger and younger to cope with the leadersjip shortage noted above.
District conventions will be 2 days long, and primarily held in assembly halls. Circuit assemblies will be cut to 1 day to allow for increased use of the assembly halls.