Nintendo has always promoted Mario as a franchise since Super Mario Bros. originally found success but around 1990 Nintendo began to expand this into a variety of gaming plaftforms. Puzzle games (Yoshi, Dr. Mario, Wario's Woods), art games (Mario Paint), sports games (Mario Kart, NES Open Mario Tennis), reversionings of classic games (Mario All-Stars, Super Mario Bros. Deluxe, Mario Advance Series) and even spin-off platformers (Donkey Kong '94, Wario Land, Yoshi's Island).
During this time Kotabe's art was very prevalent during most of these incarnations and served as a design basis for the overall franchise. While the core Mario cast remained the same throughout this period newer characters like Wario and Yoshi had gone through some very gradual changes resulting in their current looks.
Starting at the beginning of the Nintendo 64 era Nintendo shifted their focus on 3D designs for the Mario characters. Unlike when the Sonic the Hedgehog cast transitioned into 3D Nintendo kept the overall design of the characters continuous with their 2D counterparts. During the Gamecube era Nintendo made some minor alterations to the clothing design for the Princess and the Toads. Around this time Kotabe went freelance and sparringly made contributions to the Mario franchise.
In 2011 Kotabe made his return to the games with the 3DS' Super Mario 3D Land which he contributed to the in-game 3D artwork done in the “classic” style. It was also around this time that Nintendo began to also use the Kotabe style to promote various Mario non-gaming brands (Hanfuda cars, blankets clothes, notebooks,etc.) under the “Super Mario” franchise title. This brought a resurgence in the presence of his artwork which culminated in the release of last year's Super Mario 3D World.
Super Mario 3D World is in many ways a love letter to the series as a whole bringing back many elements that Mario fans have wanted including the ability to play the Princess again in a main series Mario game, a return of the orchestrated scores used in the Super Mario Galaxy series, and of course the return of the classic illustration style that helped define the series.
While I can not find any official source confirming Kotabe's involvement in the Super Mario 3D World art it seems pretty obvious given how much the 2D artwork is continuous with his established style.
In closing, I applaude Nintendo for staying true to Mario's core image and re-embracing the artwork that is so intergrated with the Mario franchise!