Level 39.5?

With the very latest update it was removed again.
The most recent client was a downgrade replacement of a newer buggy client with an older more reliable version.
So the ability to go to 39.5 has been removed again...my guess is temporarily.

You can either use one of the 'work arounds' to get your mons to 40, or simply wait for the next update when I suspect we will be able to power up mons fully...not just 39.5 but all the way to 40 (I suspect this is what they meant to do last time).

TL/DR At the moment it isn't possible with the current client..either wait, or use one of the 'tricks'

The last update, v0.81.1 for Android and 1.51.1 for iOS, was terminated because Niantic specified that it would include a fix to the bug that prevented us from powering up Pokémon to their max CP (lvl 40). But, it didn't work, only to lvl 39.5. So, my guess is that Niantic is still working on fixing the bug. My hope is that this bug fix will be included in the next big update, maybe with the upcoming Thanksgiving event or Gen 3 release, but who knows.