Nikon is wasting numbers by bringing a D780 instead of a D760, so there is only one more Number left (if we wont see a D781 some times in the new future), maybe Nikon thinks a D7xx series will become obsolete anyway.
They can add Mk II Mk III, or X or S to the name or come up with a new numbering scheme. There are infinite possibilities. A D760 would likely have been used for a "correct the bugs" upgrade but because they added significant new features, they made a bigger change to the name.
BTW I like the removal of the AF/AE-L button because it enables me to focus on the AF-ON button without the risk of accidentially activating the wrong one. If I need it i can use FN-button.
But you can program the two buttons to do the same thing - or different things - whichever you like. I don't like the front Fn buttons for this because they're a lot harder to press and hold than the thumb buttons. I wish my cameras had two thumb buttons that I could assign to e.g. different exposure or AF area settings.
For example, I might have AF-ON activate AF with 9-point dynamic area and AE-L/AF-L to activate AF with 25-point dynamic area, or 3D tracking, for example.
Another application which I currently use for the front side buttons is to switch between action-freezing exposure settings and differnet settings for a slow-moving subject (e.g., an animal that is not actively moving). I could have autofocus + 1/1600s set to AF-ON and autofocus + 1/200s to AE-L/AF-L. This way I could always easily react to a subject springing off into a run or flying off while not using any higher ISO than necessary for the time when the subject is not moving actively.
Two thumb buttons would be preferable to me for this purpose as I never really liked pressing the Fn buttons on the front side, as I lose the firm hold of the grip when I depress a front side button (to press and hold the button, the camera is no longer held from the grip but from the Fn button and this is less stable).