I have been watching this product category for quite a while now.
I work in the natural resources field and have been looking at capturing and handling data collection digitally for several years. We have had a few starts and stops, but at the end of six years we are still using carbon forms and clipboards.
Apple has a history of holding back in a product line until they can blow everyone else out of the water. The 2 in 1's just haven't really found their place in the market quite yet. They seem to be too heavy and fragile to be truly portable and too underpowered to be a good laptop. I don't think Apple is worried about cannibalization of their own market. I think they are worried about rolling out a product that is a game changer, that redefines the product category or at least adds something significant to the conversation. Look at the new MacBook. They could have rolled out an underpowered, low cost MacBook Pro any time, but they totally re-engineered it keyboard and all. Love it or hate it, it's something new.
I was playing with an HP Pro X3 the other day for our digital project. Our state IT department said another department had successfully deployed these in the field. Their idea was we could replace our laptops with these and save money. I was really disappointed. It was too heavy, too fragile, and the screen was too hard to read in full sun. The ports were exposed on the edge I would hold it meaning they would get gunked up with the oils and dirt off my hands. There was no case or straps available. I would be very unhappy carrying this thing through a tree nursery for 4 or 5 hours. (I think IT's definition of "field" and mine are two totally different things...) Put it in the office and it was terribly underpowered. A few of our guys do a lot of GIS work. These things would choke on our graphics needs.
So far, iPads or some Android tablet comes the closest to fulfilling our needs in the field. I have been rooting for iPads or iPhone 6+'s but IT has been rather Apple-phobic. (And Tim Cooks comments about a recent Indiana political issue didn't help matters, frankly.)