Cereceda's quadratic recoloring diameter conjecture for degenerate graphs

Let $G$ be a $d$-degenerate graph, and let $R_t(G)$ be the graph whose vertices are the proper $t$-colorings of $G$, with two colorings adjacent when they differ on one vertex. The $t$-recoloring diameter is the maximum distance between two vertices of $R_t(G)$, with disconnected $R_t(G)$ having infinite diameter. Cereceda's conjecture. The $t$-recoloring diameter of $G$ is at most quadratic when $t \ge d+2$. This would improve the known connectivity result for $d$-degenerate graphs to a quadratic bound on the number of single-vertex recolorings needed between any two proper colorings; the source does not state that the conjecture has been resolved.