They'd have to compete with cities skylines (and others). The only benefit they had over it with 2013 was was the ability to upgrade buildings by adding parts to it. I'd love for Maxis to try again, But unfortunately the Maxis we grew up with is gone. The hype for simcity didn't decline. people still wanted to play it. Societies build the coffin of the francise and 2013 nailed it shut. And then a competitor came along and everyone (player and old maxis employees) jumped ship, where they are to this day.
So a new simcity/sims integration would be fun for the next generation, but it would require a radical change from what EA is currently pushing