usage of after/later

"After" does not necessarily imply time. It can imply any kind of order: in time, in space, or any kind of sequence. For example, you can say that "Rob was after Sarah in the cafeteria line" or "Z comes after A in the English alphabet."

"Later" does imply time. You can say, "5 o'clock is later than 4 o'clock" and "She saw me later in the day." You would not say "Z is later than A in the English alphabet."

So in that sense, both or your example sentence use "later" and "after" correctly, since after can imply time (as well as space or sequence). However, the second construction sounds better to my ear. It's hard for me to say why. It may be related to the mixing of tenses in the sentences. They start with present tense ("It is...") but end with future tense ("...will be..."), so using the word "later" is more specific and helps make the temporal meaning of the sentence clearer.