The news comes from a Facebook status posted by Insomniac Games stating the following:
We know you’ve been asking about and waiting for Full Frontal Assault for Vita.
Insomniac cannot make any comment about the game. We have repeatedly asked Sony and Tin Giant for an update to share with our fans. They have not provided any update we are allowed to share.
We are sorry for any disappointment, but there is nothing we’ve authorized to release publicly. Trust us in that we share your frustration, and have been passing your comments on to Sony, we also advise you contact Sony directly to share your disappointment and frustration.
As soon as they give us an update we can share with you, we will.
No further news has been posted so far on the status of why Sony may have decided to pull the plug, though Insomniac Games commented that they are not the developers of the Vita version and that they are now focused on new content, maps and skins that will go into the PlayStation 3 version of the game which they are developing.
You can view the Facebook post here.