Source: Kotaku
By the end of fiscal 2018, Sony will not be making any more games on card for the PSVita in Europe or North America.
All Vita product code requests must be in by 6/28, & final purchase orders by 2/15/19. Fiscal 2018 will end on 3/21/19.
I'm not going to blame mobile gaming for this, nor the Switch. It's all Sony's fault. Surely, they killed the Vita with those damn high prices on proprietary memory cards.

