2 things, that may ease this and actually make releasing on the same day a great idea.
- For those that don't own the Vita yet will have the opppurtunity to buy a Vita and get AC3 Liberation for free.
[*]Ubisoft has not announced plans for their Collectors Edition. So it is entirely possible we could see the Vita game packed in with the PS3 collectors edition. At the very least I would expect partnerships with retailers for buying both for $80. However, a Collector's Edition may have more impact, especially if priced right.
Another thing is Marketing. Marketing is expensive, and judging by the press conference Sony has partnered with Ubisoft to make them the lead platform for marketing AC3. By having both games release on the same date and with the possibility Sony would be the focus in ads it makes it to where both games can be advertised simultaneously in ad, especially if their is a bundle or Collectors Edition. Imagine a 30 second ad, that also showed 5-10 seconds of Vita gameplay, and mentioned at the end how you could get both for one price.