We can't answer that, but we can tell you this: a developer on the XDA forums has leaked a version of Lollipop for the Galaxy S5 that adventurous users can install right now.
This isn't recommended, but for an unfinished version of the Galaxy S5's Lollipop to be released may indicate that the official version is about to arrive.
Just can't wait
The developer warns that the software is for the Sprint version of the Galaxy S5, and that it's likely unfinished.
Installing it in this form will wipe all the data from your phone, though the dev says calling, texting and other core features will remain functional.
Nevertheless it's probably best to wait for the official over-the-air update from your carrier - whenever it may arrive.