PlayStation Japan will shortly end production of the PlayStation Vita, according to the official PlayStation website in Japan.
According to a translation by Gematsu (thanks, GI.biz), just the PCH-2000 ZA11 (PS Vita Black) and PCH-2000 ZA23 (PS Vita Aqua Blue) SKUs now remain available, and shipments for those too "are scheduled to end soon". While no specific date has been given, Gematsu notes that when Sony ceased the production of the PlayStation 3, the same website made a similar statement to the Vita one above just a few months before the PS3 was finally withdrawn completely.
We knew the PS Vita was nearing the end of its life when last September, Sony Interactive Entertainment senior vice president Hiroyuki Oda confirmed the handheld would continue to be produced until an unspecified point in 2019. While some clinged to the hope Sony would look to replace its handheld PlayStation, Oda confirmed at the time that "currently, [Sony did] not have any plans regarding a new handheld device".
Sony had already taken the Vita out of its future plans with regards to PlayStation Plus’s free games, and the company advised developers and publishers it would no longer be producing physical copies of games for the system by the end of FY 2018 (so by the end of March 2019). Outside of the platform holder, developers - such as those behind Kickstarter game, Bloodstained: Ritual of the Night - have also been moving away from the system.
A recent patent might reveal what Sony has planned for its next mobile device. A patent filed at the Korea Patent Office in November 2017, and made public in November 2018, reveals Sony Interactive Entertainment Inc. has patented an "electronic game cartridge" device. The filing has just been made public.
There's very, very little detail in the five-page document - the filing pretty much the only details that the device will be made of "synthetic resin, metal" - but from the few diagrams provided, it appears that the device will connect to/from a USB or HMDI port at one end.