Two Yemenites told me they speak Persian but Google says Yemenite Jews spoke Judeo-Yemeni Arabic, a distinct version of Arabic, so I don’t know what they really speak between each other…but anyway, doing some research, it seems as if the Yemenites also pronounce the ches as hes. I guess Mizrachim, not Sephardim say/said hes.
Anyway, getting back to the topic of Yiddish, it’s definitely not going away and English is not taking over Yiddish at all. Everyday spoken Hebrew is very successful these days as a Jewish language. English is only only a first language for America and Candian with the exception of most Chassidishe.