Cryptocurrency mining WILL crash, it's just a matter of when, and it will slaughter both AMD and nVidia stock prices when it does.
But no, IGPs will never catch up to dedicated cards at least in traditional computers, as aside from the thermals, there is the problem of power and space. They will, however eventually, run up to pace with couple of generation old high end cards. Vega M GL inside the i7-8705, for example, is of the power of the mobile RX 550.
Space is the number one problem, as you need a footprint the size of the i7-8705 to fit memory, GPU, and CPU cores all together, which means it's going to be its own socket.
Power is another problem, since you will need something along the lines of 150 watts to feed the GPU and memory, and that's on top of what goes to the CPU, and that's a lot of current. It can be done of course, Skylake-X and the FX-9000 series showed it, but that requires beefier components which drives up the price. And of course thermals will be an issue. All this leads up to something which isn't a drop-in replacement for traditional sockets, so while it may be great for consoles, as far as desktop APUs go, it's a no go.