Lol he's 46, don't worry so much.
Sure, I see the final "plot" taking as long as this last Yonko plot did, but it'll probably be far more focused imo. No more Doflamingo's or Caesar's or Katakuri's as main villains and characters, now you have your Vegapunk's, Dragon's, Akainu's etc all at the helm with the last 2 Yonko.
Basically post-Wano will probably start to set everything up ala Punk Hazard, but it will focus on those we know already in the series. Whether Vegapunk is next or Elbaf or whatever else, he'll still be building up to that final war in the end, just like how PH, DR, Zou, and WCI all built up to Wano.
Imo, either both Yonko are centric to the final war with Akainu/Im, etc. Or Blackbeard is the last fight (at Laugh Tale) before the final war, and Shanks is part of the Final War and post war (i.e. maybe something like God Valley).
Basically Oda needs to build up the final war for several arcs, get the final RP for Luffy, travel to x amount of islands before Laugh Tale, do Laugh Tale, then show us the real motivation behind the final conflict. We already know some portion of the final conflict must include Fishman Island, so likely Mariejois and New Marineford are going to be fronts in that War. Not only that but God Valley has been teased as something signficant that Oda hasn't revealed yet. There is still IS a lot to go, and it's the perfect way to set up the last 2 Yonko/Akainu/Im/Dragon/Vegapunk/Elbaf stuff.