Kottwitz's trace formula conjecture for regular discrete series representations

Let $G$ be the reductive group under consideration, let $\pi$ be a regular discrete series representation of $G(\mathbb{R})$, and let $e_{\pi}$ denote the stable cuspidal test function associated with $\pi$ as in Section. Choose a compactly supported test function $f^{\infty}\in C_c(G(\mathbb{A}_f))$, with measures satisfying $dg_f\,dg_{\infty}=dg$, the Tamagawa measure on $G(\mathbb{A})$, and set $f=f^{\infty}f_{\infty}$, where $f_{\infty}dg_{\infty}=e_{\pi}$. Kottwitz's trace formula conjecture. One has

$$\operatorname{Kot}(f\,dg)=\operatorname{tr} R_{\operatorname{disc}}(\pi,f^{\infty}dg_f).$$

This predicts that the stable trace formula with a regular discrete-series test function isolates the corresponding discrete automorphic representation's trace. The surrounding discussion establishes the analogous identity after summing over the relevant discrete-series packet, while the assertion for an individual regular discrete-series representation is presented as plausible and remains unresolved in the supplied text.