so, where are the speculations?
here mines:
1- foldable screen, The next handheld system will have a sinlge foldable screen, and it can be used as a 3DS if you fold it in the middle, and can be used as a secind gamepad.
2-all graphene tecnology in processors. So the next home console will be 1000 times faster than ps4 and cheaper, and no other company can use graphene.
3 - QoL related: will be like a mix of wiimote and a cellphone. you can carry it for everywhere, but you cant wear.
d-pad and 2 buttons for easy play, and also a touchscreen. it will have lots of high precision sensors that monitor position, acelaration press, and even feelings(and this is the tecnology bought), there will be also a mini hdmi dongle to connect to tv and you can play games like wii sports in any tv.