The boundedness-of-index conjecture for canonical Q-Fano varieties

Let $W$ be a canonical ${\bf Q}$-Fano variety of dimension $n$, meaning that $W$ has at worst canonical singularities and $K_W^{-1}$ is an ample ${\bf Q}$-Cartier divisor. Its index $r(W)$ is the maximal positive rational number such that $K_W^{-1}=L^{\otimes r(W)}$ for some Cartier divisor $L$.

Boundedness-of-index conjecture. The set of possible values of $r(W)$ for canonical ${\bf Q}$-Fano varieties $W$ of dimension $n$ is finite.

The source presents this as the additional conjectural input for deriving the Spectrum Conjecture from the Minimal Model Program. The supplied text gives no resolution status.