There's no official word from Rockstar on this, so we don't know of any release dates or pricing information. We're also not sure why San Andreas has curiously been left out, and/or if it may appear at a later date.
On a slightly related note, this year will be Vice City's 10th anniversary. If Rockstar are planning similar things to what they've been doing for GTA3, it wouldn't surprise me at all if we see Vice City appearing on iOS and Android later this year either.
Thanks to R* Network for the heads up.