How would I make a slow motion face morph between two faces (with example video)?

Sure as Szalam says you could use an iPhone 7 in slow motion of 240 fps in HD and you could apply a Frame Blending / Pixel Motion to make it even more fluid. The blink if you must do it separately.

I'm not sure you can achieve it with Displacement Map, what do the ACP partners say, will it be possible?

The blinking really looks faked/not real. I'm not sure it's a slo-mo shot because of that.

That said, a slo-mo shot would be the easiest/best way to do this. If you have an iPhone 7 or later, you can do some really nice HD slo-mo stuff natively in the phone which you could import to AE to make slower or faster as needed.

If you must do a morph, you could just take a smiling face and use Liquify to make it look frownier then animate the strength of it down so it unfrowns. (Which is kinda what it looks like they did here in addition to adding wrinkles to the forehead.)

If you want to do an actual morph, there's a tutorial on CreativeCOW for morphing with AE's built-in tools. If you need more power, Re:Flex is the industry-standard for morphing in AE (it's an oldie, but a goodie): https://revisionfx.com/products/reflex/

That's just  a slo-mo shot of a guy smiling.  No morph.