Can I use a keyboard to play Minecraft on PS4?

Just buy Minecraft on the Wii U

You might be able to, but I wouldn't know how. You can, however, connect the USB on the keyboard to the PS4 so you can type easier.

No, not until it gets the "better together" update that all the other consoles got -- and which Sony has so far not allowed to be ported to the PS4 because of the need to sign into a Microsoft account and their refusal to support cross-platform multiplayer.