Complete Collection includes an updated version of FFIV, like the freshened-up Final Fantasy and Final Fantasy 2 released on PSP, with fancy graphics for spells and new character portraits, combined with 2D character models. The After Years is presented in the same style. The Complete Collection is slightly more complete than just the two games on their own: it also includes an exclusive story connecting the two.
It'll be released in Japan this spring. There's no reason not to expect Square Enix to localize this Final Fantasy game, so it's only a matter of time.
[Image: Final Fantasy IV: The After Years (WiiWare version)]