ARMS, Nintendo’s experimental, stretchy-armed arena fighter for the Switch has received a new update; the contents of the update, which brings the game version up to 5.4, have not been revealed — however it may point to new content for the game in the future.
The announcement of the update comes via the official Twitter account of ARMS‘s in-game commentator Biff. Alongside the announcement of the update, Biff teases what may possibly a new character for the game.
— ARMS（アームズ） (@ARMS_Cobutter) September 18, 2018
In the tweet above, Biff mentions Dr. Coyle (head of the ARMS Lab) being busy in her lab, and talking to an unknown person in it.
Additionally, the Nintendo Switch Online service has started this week, so it’s likely that the update is related to that as well.
Source: ARMS Cobutter