McDonald's introduces a new French Vanilla Latte this holiday season to their McCafe menu, except it might not be "new" at all, but might be more like new to appearing on the menu.
According to an employee at my local McDonald's, they use the same vanilla syrup that they use for the rest of their McCafe beverages (it is also possible my local McDonald's jumped the gun and started offering it before actually getting the new syrup, if there is one). So basically if said employee was correct, it's just a Vanilla Latte, which technically wasn't on the menu before (they've always offered a latte with a choice of syrup if you so chose).
Update 12/1/12 - McDonald's confirmed that the syrup is a newly-developed syrup with a "sweet, creamy vanilla flavor."
Update 10/31/12 - I stopped by another McDonald's in my area. The menu board now only offers "French Vanilla" and "Sugar-Free French Vanilla" syrups with no mention of plain "Vanilla" syrup.