Prediction: it will be a long, steep enduro boulder in Switzerland originally discovered by Dave Graham in the mid-2000s. It'll be at least 5 years - I think V17 will need to consolidate before anyone feels bold enough to propose V18.
Agree with this sentiment, 1oo%. The strongest names in the sport suggest V15 leading into V16 climbing without rests. It'll be bold for someone to come out and claim the grade, and naturally, it'll be downgraded countless times or given a solid score once it's repeated. The kids are SO strong these days; it's truly impressive to see where our sport is going!