Is the F-14A playable in Ace Combat 8?
Yes. The F-14A is a confirmed playable aircraft included with eligible preorders.
Confirmed explanation
The aircraft is listed separately from the Ace Combat Zero bonus game and from Deluxe Edition benefits. Publisher notes also allow for bonuses other than the Zero port to be released later, so preorder status does not prove permanent exclusivity.
What is not confirmed yet
Stats, special weapons, campaign timing and a later acquisition route are not yet confirmed.