I don't think Sony needs a new handheld...
Vita is a beast, they only have to support it and make some changes...
- Allow multiaccounts, just like ps3/ps4: You know, it's a s***... when my brother picks my Vita he has to restart the system, adjust time/age/date, he has to watch the f***** video, connect to the Wifi, write his PSN account, and after 10min he can play with his account! Then when I want to pick the Vita again, I have to do the same. Worst decision ever made by Sony on Vita.
- Give Vita some games that ps3 or ps4 don't have: They have lot of abandoned Ip's (The Legend of Dragoon, The Getaway, Medievil, Omega Boost...)
- Allow any SD card not only Sony. If they don't like this, then drop the price of their SD cards or bundle 16gb+vita for a reasonable price.
-Bundle Vita+Ps4.
These changes + ps4 remote play and I'm 100% confident the sales would increase.
If someone here works for Sony give them this information :D