Ive said it before, but sony needs to do 2 things to remedy this situation but they may prove expensive.
Mandate every PSN release from here on in must have a PSvita version outside of PS3 GOD releases and DLC/Expansions.
Give devs all the support and dev kits to make this happen.
Likewise, Find the most profitable and highest rated PSN releases and approach those devs in thinking of making a Vita version.
Imagine Flower, Ecochrome , pixeljunk eden, Crash Commando , Cubiod, Castle crashers, Scoitt pilgrim etc on the device
Im not saying sony should be concentrating solely on ports of PSN titles, but that would do alot more to bring people on board the platform, and while would need some dev time wouldnt need as much as a brand new I.P from scratch.
There is No excuse in my mind that games like journey, Sonic 4, Hell Yeah! and Zen pinball dont have vita ports in the works, even if they are released significantly later.
Vitas future does not lie in Retail AAA titles, downloadable or not. It lies in smaller titles, more substantial that the app store, but still significantly cheaper/shorter/more pure gameplay-focused than PS3 titles. £20 max.