The novel series’ “final season” ended with Zoku Owarimonogatari in September 2014, but it featured a teaser for “Monogatari Series, Next Season Tsugimonogatari.”
The manga went on hiatus on July 31 “for a number of issues” due to Oh! great’s sudden illness.
The July announcement noted that Oh! great is slowly recovering and is preparing to resume the manga.
The novel series’ new “Monster Season” launched with the Shinobumonogatari novel in July 2017.