I worry about Wayland for the features it drops from X11. Wayland will never have xdotool support, due to its security model. I worry about onscreen keyboards for drawing tablets and screen readers for the blind.
ydotool is missing a lot of features. It emulates an input device, so it can only send inputs to the active window. xdotool can send keystrokes to non-active windows, and has features for searching for a window to send to. xdotool can minimize, dismiss, or move windows around.
I'm aware of newton. It's a work in progress, though, and doesn't have as many features as X11 accessibility has. Although it might have enough features eventually, I worry that X11 will be deprecated by operating system vendors before that.