On Japanese television there have been reports of test runs that will take place in search of a replacement for the 381 series on the Yakumo limited express service. The television program shows a JR Shikoku 8600 series, although according to one of the comments on the Facebook post there have been test runs with this train type on JR West territory already last month.
Source: https://www.facebook.com/groups/lovekokutetsutype/permalink/1482471928487919/ (JNR fan page on Facebook)