It appears that JR East will be building a new experimental Shinkansen EMU in the near future. The set will be called ALFA-X (Advanced Labs for Frontline Activity in rail eXperimentation) and be built in 2019, besides general technological advances and improving winter operations it appears that JR East will attempt to determine feasibility of increasing the operating speed of Tohoku Shinkansen to 360 km/h
http://www.jreast.co.jp/press/2017/20170705.pdfOn less exciting news, it seems that JR East has decided on what DMUs will be replacing the KiHa 40 series DMU
Hachinohe Line: KiHa E130-500 DMUs (entering service later this year)
Niigata / Akita Area: GV-E400 Diesel-Electric DMU
For GV-E400 DMU, the pre-production set (1 single car set and 1 two car set) will enter testing in 2018 and enter service in 2019 for Niigata area and 2020 for Akita area. An open tender was issued by JR East but we don't know who is actually building them yet
http://www.jreast.co.jp/press/2017/20170706.pdf 