Absolutely stupid. It would make the ipad useless for music creation with attached devices like the Apogee JAM. Why? Because of the wireless audio playback via headphones, there will be a significant delay and high latency compared to cabled headphones. Which with wireless audio makes playing and recording instruments like guitars, drums, and other things, completely useless.
There is NO way around it. No bluetooth based audio has the necessary low latency required for these types of uses.
I can understand the removal of the headphone jack on a small phone, but on a tablet designed for the "pro" market it literally does not make sense AT ALL, and would be a tremendously STUPID decision, and a big slap in the face of the users that ACTUALLY uses the iPad Pro for anything that revolves around CREATING rather than just consuming the latest games and youtibe vidz.