But in reality you have bi-modal IT, either by purpose or as shadow IT when business units develops their own solutions outside IT or everything thats is BYOD. This is not a new phenomenon and I was employed more than twenty-five years ago by the business to implement new systems outside the realm of the existing IT.
So the question is not if you should have bi-modal IT. The question is if you need an IT-department to take care of the older stuff that is not modified som much. If you delivering digital services to your customers, this is your main business and not a task for the CIO. Of you are delivering non digital services or products as your business, then IT doesn’t matter and you don’t need a special IT.