I'm gonna be honest. I pull from many sources and make a combined decision
EasyWDW
Touringplans (I don't subscribe, but if I can remember I check their free preview at about 45days out)
Undercovertourist
************** has a really nice week-view calendar
Dadsguidetodisney
They typically each have something a little different to say, and since they're all just educated guesses I use them all to make my own guess