What is the opposite of "Expiring Soon"?
Solution 1:
For your example of sorting a user interface, I would use superlatives:
- expiring soonest
- expiring latest
It's difficult to find an opposite for soon that is useful because it's not specific enough. Using superlatives, in this case, tell us that we're looking at the dates in question, not some subjective notion of what soon means.
Solution 2:
"Sort by: Expiring soon" sounds like a Boolean. I think that to express what you actually want to do you should look at terms like
Sort by:
- Expiring soonest first
- Expiring latest first