On the one hand: not free for a game not even 6 months old (will be 7 by the time of the upgrade though)
On the other hand: $10 instead of full price
On the third hand (thank you C button): Activision gonna Activision
Free upgrades are a great gesture, especially for anything released within the previous year, but should not be expected. Business and consumer-wise this is the least offensive option since they're basically doing this to upgrade anyone with standard to have the extra content form the DLC/DE bundle as well as the next (now current) gen features.
I'll be doing this just to be able to do 1080p120, at the least. The spatial audio will be nice, too, if they mix it properly.