Which skill set should we focus in current market....

What do we mean by backend + ai / ml. What's ai ml here

All 3. People really underestimate how important that is going to be in the age of AI.

Also why do we think front end being the first? Umm has anyone here actually dived into web, mobile apps both?

I believe frontend would be the first target of automation. AI is already smart enough to create a decent frontend, it'll only improve from here.