Reading up on it a bit the headphone jack is literally the biggest component inside the phone. It is what is preventing phones from getting thinner/lighter, not to mention batteries getting larger.
Yes they will make money off selling adapters but it also paves the way for thinner, lighter phones with the possibility of a larger battery. The headphone jack has remained basically unchanged since its inception like 50 years ago, I don't have a problem with it finally being upgraded.
Hmm no way to make the jack smaller? If that's the reason to get rid of it then well ya go for it.