The next Skylanders game is expected to come out at some point during this year. As of this point, little is actually known about the title, though Activision has stated that it will be innovative. Some new rumors by Liam Robertson seem to suggest a rather bold change to the series.
According to Robertson, the next Skylanders game will include the use of vehicles. The game is allegedly in development for all major consoles. We should expect to hear more at E3 in June.