Try all you want, you won't be able to shove your UMD games into the upcoming PlayStation Vita. Like the PSP Go, Sony's next handheld is completely digital, and won't be compatible with the PSP's disc format.
Sony has a solution--at least for gamers in Japan. The "UMD Passport" program will grant gamers access to the PSN versions of their disc-based games... for a fee.
Beginning December 6th, Sony will release the "UMD Passport" application on the PlayStation Store for PSP. The program will detect games in the UMD drive, and will unlock the ability to purchase a PlayStation Network version of the game at a discounted price.
Not the entire library will be supported by the passport, as there are a few titles that were never offered digitally. About 200 titles will be supported by the passport, including games like Gran Turismo, Patapon 3, Disgaea 2, and Persona 3. The re-purchase price ranges from 500 yen ($6.46) to 1000 yen ($12.92).
You'll be able to play all PlayStation Network versions of PSP games on your Vita, with support for upscaling to make games look even better on your shiny new handheld.
SCEA has not announced a similar program for America. We've contacted them to find out if there are plans to implement a "UMD Passport" in the States as well.