II'm not sure he is positive that he really wants to go to his dad's place, but I'm not going to say any more unless he brings it up.
I get that with my son as well. Yesterday my son was saying "oh we could go to the halloween fun day on Saturday, then have lunch out if you like!". I have to remind him a couple of times in the week that he is staying over at his dad's on Saturday.
H47 me48 T22 M21 S20 - Got high functioning autism 3/2000 H admits to OW and moves out to live with her 11/2000 H moves back home 2/4/13 H moves out H tells me he wants D 6/13, but now he can't afford to!