The few sites that kept up with G4 are no longer getting updates for some reason.. I used to use Strawberry Reef but it's several waves behind and was last updated early 2015... My Little Wiki only goes up to 2014... the MLP Arean's web page for New and Coming soon only goes up to items being released in 2015 as well (which in that list was mostly plushies)
MLP Merch is the only site that is keeping up-to-date of what is being released but it's not an actual list