A deal breaker *for you*, and for some reasons you failed to elaborate.
For semi-professional use, or hi-end headphones, there are fantastic DAC lightning interfaces that sound an order of magnitude better than the Cirrus Logic found on the 6S.
For casual listeners, Apple will provide good enough lightning earbuds or, as I suspect, BT5 AirPods.
Finally, for those already on premium BT wireless headphones, nothing will change, but a better, stereo sound out of the onboard speakers.
No deal will be broken in the process.
And a non-deal breaker *for you*. Classic displacement, think as I do or you don't have an argument.
We can agree at least that each other's anecdotal experience may not be the candidate for the absolute truth.
*Personally*, removing the 3.5" from an otherwise unchanging phone is a deal breaker. Next to that, between the casual listeners and the deep-pocketed audiophiles, you seem to have eliminated all the in-betweeners who may be happy with eg. a pair of wired Sennheiser Momentum cans and can't or won't deal with another dongle or DAC, for the sake of price, practicality or whatnot.