Drton–Sturmfels–Sullivant conjecture on the ML-degree of cycle graphs

Let $C_n$ be the cycle graph on $n$ vertices, and let $\MLdeg(C_n)$ denote the number of critical points of the Gaussian log-likelihood function for generic sample covariance data, equivalently the maximum likelihood degree of the corresponding Gaussian graphical model. Drton–Sturmfels–Sullivant conjecture.

$$\MLdeg(C_n)=(n-3)\cdot 2^{n-2}+1.$$

This conjecture predicts the observed ML-degrees of cycle graphs and gives an explicit formula for their algebraic statistical complexity. The supplied text does not state whether the conjecture has been proved or disproved.