Yes, it was terribly kept secret. Apple telegraphed an iPhone arriving without a standard headphone jack for years (I mentioned it myself two years ago), and there are enough Bluetooth headphones out there to satisfy the casual music listener without issue. Folks totally attached to the wired experience even get an adapter to mitigate the transitional period.
However, this change does adversely affect the iPhone-based music makers. Bluetooth simply introduces too much latency into the workflow to make wireless headphones effective. Doesn’t matter if you buy the new AirBuds or use your favorite third-party model (and you should, ’cause Apple doesn’t have a great history with headphones). If I notice the noise of a bone-crunching Madden hit well after the play occurred visually, the response of my Minim pad will definitely not cut it. And if you use the adapter to connect your favorite headphones, you have to hope your battery is fully charged. The headphones just took your power jack! The music apps I’ve used don’t seem to drain power the same way the aforementioned bone-crunching hits do, but it’s still going to impact power usage. At this point, I’m obliged to remind you to put your phone in airplane mode for more intensive musical pursuits.
To be fair, the iPhone probably isn’t your primary music platform, and if it is, grab an iPhone 6S+ while you can. The headphone jack removal isn’t too big of a deal, but it will make mobile music creation a little more inconvenient. iOS remains the best option for mobile music making, though, so it’s an inevitable inconvenience.