Sony’s said that it has no plans to bring PlayStation 2 or PlayStation 3 support to the PS Vita at this time.
Speaking in an FAQ published on the PlayStation Blog, the platform holder said:
Users can play supported digital PSP titles and supported Minis [on the PlayStation Vita]. In regard to PSone classics titles, we will announce further details when they are ready. PlayStation does not have plans to make PS Vita compatible with PS3 or PS2 titles at this point.
PS2 support was always a long-shot, but the good news is that Sony isn’t ruling it out entirely. Is this a feature you’d like to see focused on in the future?