Personally I think Apple will at some stage have to make a second tablet aimed at a different audience or they will lose custom.
There does need to be a, and I'm not being rude, dumbed down, very simple interface, with 1 app at a time, full screen like we have now.
All the grannies, and people who are not interested in "computers" will want this type of device. However, they are, and will be another large group who want a tablet, but also want more.
If Apple don't offer it, then in time someone else will.
Perhaps we will need multiple apps in multiple scalable windows on the screen together? Or different input device options for more high end work like Photoshop / Cad type work.
iPad Pro some have said. I don't know, but I don't believe 1 tablet can be everything to everyone in the long term.
Such a tablet is being offered now and I don't believe Microsoft or Windows OEMs are too thrilled with sales.
iOS will become more robust and will become more feature-rich, but Apple tablets will most likely continue using two important features: full screen apps and a curated way of obtaining apps.
I would say, and I would suggest Apple would say that if you want a compact and lightweight device that handles multiple windows and multiple input devices that you should buy a MacBook Air.