I really hope Yamaha will not do so. When connecting a single device (Genos) to a host I really prefer one USB cable over two of them. Your mileage may vary.
Yamaha arrangers have 2 midi ports in order to allow to reproduce a midi file with the internal midi player (that could saturate 16 channels) and at the same time allow the user to play in real time above the midi file playback (another few midi channels needed) using the built-in keyboard.
In this use case midi in/out is never used.
The midi in is needed when you use the arranger as a sound module ("expander") driven by a PC (sequencer). In this use case 16 midi channels are usually more than enough. Especially if you consider that Genos & Co can only mix down all the incoming midi channels into a single analog audio stream, output trough the onboard speakers and/or analog audio jack.
Who realistically needs 32 input midi channels (= a jam of 32 different instruments) mixed together by the keyboard into a single audio stream?
To say it all, probably the few using the Genos & Co as an expander will only send a single channel at a time (and record back the audio into a DAW). When all the recordings are made, the final mix down is done into the DAW with all the bells and whistles it can offer (including a full stack of effects applicable separately to each channel).
Our software (
www.groovyband.live) on the other hand sends up to 16 channels altogether (8 accompaniment parts, 4 parts from the first manual, 4 parts from the second manual + pedalboard). And the result is crowded enough that you really do not need more. And anyway you will be limited by the sound generator polyphony (notes drop out) or DSP effects (audio quality).
So in my opinion a single
class compliant midi port is the way to go. I respect your opinion though. If you really need 2, then a second class compliant usb cable is an option. OR you could offer 2 ports on a single midi cable with a proprietary driver (for the very few who actually need 2 ports).
Proprietary drivers have the bad habit of not being updated when the manufacturer goes out of business or when it has no more economic interest to support an old out of production product. As a matter of fact, products tend to out live their proprietary drivers.
And the world is full of perfectly usable devices whose drivers have been only updated to, say, Windows XP. And hence they must be scraped because they are useless on modern PCs.
To make things worse, Yamaha does NOT provide any driver for Android devices, which represent the vast majority of mobile devices out there, and certainly the future.
You can probably sell a 4k€ device to a ~70 years old wealthy man, asking him to install a 1990s proprietary driver in his old fashioned desktop PC. If you want to sell something to a millennial, to start with you cannot ask 4k€, and then it must connect hassle free to his smartphone.
If you fail to do that you are out of business. Period. And things happen fast (before 2008 the smartphone did not even exist!!). And if in 2020 you are still selling a product designed in the 1990s then there is a problem.
It is hard to be a "brick & mortar" XX century company selling electronic devices in a market where software, web, and interconnections are the king. The gigantic failure Yamaha incurred with their e-commerce web site when they wanted to offer a free download of their expansion packs says it all.
In any "digital" company the responsible of such an epic failure would have been court-martialed on the spot, and directly sent to the firing squad. But if you are brick & mortar you do not even see the failure, and hence do not even feel the need to apologize for that.