Pretty much this.
Right now we get around 35-38 chapters per year. Oda's comment, that he would like to finish OP in five years, was made a year ago.
That would mean that we have ~140 chapters left.
Totally unrealistic imho.
Wano alone will last at least 50 more chapters (we're still only in act 3 and the countless fights haven't even begun yet, fellas).
That means in this scenario there would only be ~90 chapters left for:
1) Elbaf (we are definitely going there, make no mistake)
2) finding Laugh Tale
3) final standoff against the BB pirates on Laugh Tale
4) learning the secrets of the world at Laugh Tale and Luffy becoming PK
5) leadup to the final war against the WG/Im-sama
6) the biggest war the world has ever seen against WG/Im-sama
7) conclusion of the story and epilogue
No way Oda manages to do all this in only 90 chapters. It would be devestating, considering that ordinary arcs like Dressrosa or WCI alone lasted 90+ chapters.