You'd be surprised my friend! The future holds so many surprises.
Who would have thought the iPad would've been invented. I didn't! I said it would just be a fad and would flop hard and it's useless. Now they're everywhere.
I can see the Apple Watch just getting better over time. I can see I being s stand alone device in the future I can see it having cellular service and making phone calls and essentially replacing your phone. Maybe in the near future 5-10 yrs we'll be rocking apple watches and iPads only. Who knows.
Actually I think the iPad was seen in the "slates" that were out before that. I'm not sure of the time line, but I think there were several slates well before the iPad. It seems Apple just waited until they got it right with the size/weight/thin...
As far as the watch goes, TBH, I just don't see it. It's far too small to do much. Apps will be very limited in function because of the limited screen size and ability to interact with the screen.
What we'll see is a cross-over of product functionality. Remember, Kodak had 770,000 employees and digital cameras, the functionality of the digital camera is not embedded into EVERY smart phone as standard equipment.
This is actually the same problem as the watch, the classic functionality of all watches have been embedded into most any entry level smart phone. From a product stand point, this is a very rare step into the past products.
The smart phone does everything the watch ever did, now they are trying to get some of the function into the old form factor. Huge risk. I can't see any compelling (beyond "me too") for any small form factor wrist device.
Just as much as the iPT/iPhone/Mini/iPad/iPadPro... overlap in function, difference in form factor. It's like someone owning 5 different cars, sports, compact, sedan, SUV, pickup... in the end, it's just too complicated. Esp from a company that used to focus on making life simple.