Didn't realise it was that strong but how much of that was because of piracy support, ultimate emulator/pre-smartphones, MH etc...
Japan was the healthiest market for PSP software. While there's no doubt that piracy hurt some games, I doubt any Japanese publisher turned their nose to the platform because of that. As for Monster Hunter it obviously played a huge role and shows how Sony has failed with Vita. No exclusive Final Fantasy, Metal Gear, or Monster Hunter titles on the handheld with no chance of that improving.
Price cut will have some software at the very least, killzone and tearaway. Cod was a joke, killzone isn't the best brand franchise, but the vita is an fps machine without an fps. Cod had a better chance but it was quite early and we also know how it went and likely why. Let's not rule them out yet. We may already know about Killzone but I bet they want to go after more than just people casually aware the vita exists, so its release should have a lot more effect than its announcement. Although, GTAV :/
Killzone is a niche franchise and Mercenary will be sent to die as a casualty of Sony having too much to market and not enough ad dollars for it all. Tearaway will suffer a similar fate due to being a new IP. Sony's not going to land a new GTA, or an exclusive entry in some other well known western third party outside of more 6/10 Ubisoft spinoffs.