Vintage JNR Trains in West Japan

Recently I saw an episode of NHK World’s Japan Railway Journal that talks about the Okayama Branch of JR West and their Kokutetsu era trains such as the 115 Series the 381 Series “Yakumo” and the KiHa40 Series. Trains are very much my thing, and I would like to ride these trains before they are gone. I know the clock is ticking for the 381 Series in particular, as new trains are set to take over Yakumo services from spring 2024. I will be in Japan this coming January for the third time and would like any insight into whether or not these classic trains will still be in operation then. If so, I’ll absolutely head over that way. If not, I’ll find other things to do for those days.