Although nothing seems to be certain in Pokémon Go, there are a few things to keep in mind when it comes to Niantic adding new, exciting features in the game:
- Niantic is working to bring players back to the game not lose more, so they won't likely do anything that would deliberately ostracize players. We've already seen this with rural players and players who live i certain countries. I think it's safe to say that the release of legendary pokémon in the game will be for all players globally.
Minor updates and event occurrences have increased to keep steady players engaged. That will likely continue and perhaps increase.
Major updates (the kind that have a large impact on the way the game is played) along with special events will probably be more sporadic (Niantic won't "play all its cards" at once).
Legendary events are likely to be just that- rare, but epic.
It seems safe to anticipate a pretty great celebration for the first anniversary of the game- especially with a promised introduction of legendaries. Don't forget, though, that there is no guarantee about which legendary pokémon will be released. Also, the possibility remains that the legendaries in each grouping could be released individually. For example, Niantic could get sneaky and introduce the legendary birds into the game but only release one at a time over a period of time. They will want to milk each event (especially legendary events) for all they are worth.
I've rambled on long enough. Thoughts?