Imaginators is a neat concept and a good next step for the franchise but probably isn't lighting the world on fire.
Activision did this with Guitar Hero though where they saturate you with a game every year (or more). Then you get bored of it quickly. I'm sure after the first Skylanders or two they saw dollar signs in their eyes and you can't blame them for wanting to continue to pump out games yearly but they need to have the foresight to space these out a little. Probably could have went every other year after Swap Force.
Then again, what do I know? Maybe they had the market research that it was going to die in 2016-2018 regardless of release schedule so milk it while you can?
It wasn't just Activision
Lego, and Disney jumped on the band wagon, quickly over saturating the market.
Add to this, instead of letting the games cook for a while and growth, they make you buy a new "Starter" pack every new game, along with new portal, etc, etc, ignoring most of the previous figures, then you have problems.
Games 1-3 allowed you to use your previous characters top open and do 75-80% of the game.
Then 4+, only the new figures could access the locked areas of the game.
This is also coupled with the idea Supercharges was marketed wrong. The game was a traditional Skylanders, but marketed as only a kart-racer. Even making the Wii (the highest selling Skylanders console) and 3DS versions Kart-racers only.