How do I change my team?
Unfortunately, it is not possible to change your team at this time. We plan to add this functionality to Pokémon GO in the future. We are working on a few other big features first, so we don’t have an estimate on when changing teams will be possible.
Indicating that switching teams will be an option at some point in Pokemon GO
I can see this could creat massive stagnet areas or a more toxic community.
Imagine an area dominated by one colour and because the opposing colour living/playing in the area struggle to hold any Gym time they decide to join the dominating team. All of a sudden there is no one one to battle them out.
The multiple accounts of opposing colours and shaving own colour would become a bigger problem. The alternative is everything stays in a Gym for massive lengths of time.
*Laughs with contempt * Very happy Instinc player here.
In my own city i dont foresee a major shift in balance. Maybe a few of the lower levels will switch. But most high levels are part of the community within their teams, so they wont switch very fast.
I would seriously consider moving from Mystic to Instinct just because almost all the gyms in my city belong to Mystic, with almost all of them with a full team.
Sometimes when I get those “battle a gym” quests I discard them on the spot because they’re very difficult to complete for me.