What happens to the reach if you wipe both the Silver Bloods and Madanach from the Reach?

I just did Cigna Mine in Imperial-controlled Markarth in my current play through were he came to reward me for killing Madanach when I realized he is the last Silver-Blood alive who still has power and I realized that I could wipe their empire out for good now that he isn’t essential.

What do you think happens in such a scenario? Does Markarth’s economy crash? Does the Jarl seize their property? Are there any other heirs I don’t know about? What happens to the Forsworn with their leadership has been literally decapitated? What about Nord-Reachmen relations?