When it's such a lucrative move to drag it out as much as possible to milk unwitting fans, then it's very likely that it could span for as much as Naruto did. And based on various facts such as the Anime premiering in April 2017 and barely covering the manga that's x10 slower in pace, we could probably have to wait for over a decade to actually see the Kawaki vs. Boruto scene. The manga has been on for 2 years now, hasn't it? And there hasn't even been a major felon to serve as a catalyst to the story. That said, I decipher it'll be another year more before the Anime actually kicks off, then a good decade before the Manga gets to the jist of the story, if the pacing persists.