According to website TheSixthAxis, reports are staring to come in suggesting SCEE have started updating older PSP titles on the PlayStation Store so they work on the PlayStation Vita. Games you have already downloaded onto the PSP or PS3 may not appear on the PS Vita’s Content Manager Application until the game has been patched.
If your PS Vita doesn’t pick up content from your existing PSP collection, you may have to download the game again and leave them uninstalled until you get your PS Vita in a just under 2 weeks.