One of the Editors said in the area five more years.
By the end of this Arc The List of things Luffy will need to accomplish are
Find The Last Road Poneglyph(you need 4 of these to get from the second to last Island to the last Island, Luffy has 2 will have 3 by the end of the arc)
Visit Elbaf the land of the Giants
Get to Roadstar Island(the second to last Island)
Go to Raftel.
If each chapter is as long as the longest arc, about 8 years at max, I doubt that though because Dressrosa was -LONG-
The ending is most definitely in sight though, We got a real glimpse of Gol D. Rodger's voyage (through the eyes of somebody else, but enough to give us an outline), Luffy is likely going to equal or surpass one of the 4 most powerful Pirates of the previous generation by the end of this arc, and the world outside of the current Island is starting to fall to Chaos, we aren't in the end of the series yet, but the next arc will be the start of the Climax.
Edit : Read the spoilers and
Bets on Yamoto being a rebellious shit head and telling Kaido to fuck off when Kaido announces he is gonna get married to one of Big Mom's children? Given they are waiting for Mom's kids to show up, and Kaido's son to show up I can't imagine that Kaido's big announcement is that Kaido's kid and one of Mom's kids are getting hitched during the festival. Which breaks up the "Alliance" in a sensible fashion and allows the battle to turn into a fantastic shit show while not making Luffy fight both Yonko at once.