Please keep in mind that TF2 already had this functionality, they are now just using a shared implementation across all their games, instead of one put into the main game code. So far, TF2 and Dota 2 have moved to this shared code, while CSGO has yet to do it for theirs, but that will presumably come with the promised Source 2 port.
As for what this indicates for TF2, it could go either way: updating the game code is confusing if they were going to move to Source 2, as it is seemingly pointless extra work but at the same time, it makes the Steam Datagram portable and engine non-specific and allows them to test the external code beforehand.
As for the Pyro Update in general, this update has nothing specifically related to it.