You need to verify that you are indeed on these new flights! Yes, they do slip up once in awhile leaving you with no reservation.
Often the airline will send you a new confirmation (usually an 8-1/2 by 11 page) that you are on new flights. Even if they do confirm your new flights over the phone, ask for a paper printout (including for e-tickets) to be sent to you if that makes you feel more comfortable.
Just my opinion, if your original flights are cancelled, you are entitled to your choice of alternate flights at no extra cost provided they are not completely sold out.
In the old days, if you took your paper ticket to the airport or to a downtown ticket office (the latter are few and far between as airlines cut frills) they stuck little handwritten paper tabs on the old tickets specifying new flights.
More Disney tips:
http://members.aol.com/ajaynejr/disney.htm
9/65
Disneyland
3/75 *World Inn (now Doubletree Club)
4/85 *Kon-Tiki (now Econolodge Hawaiian)
'80s Disneyland once or twice
7/94 Dixie Landings (now Port Orleans Riverside)
9/97 All Star Music
11/98 ASMu & first premium annual pass
12/98 *Knights Inn on 192
9/99 All Star Movies
12/00 All Star Sports & PAP#2
9/01 ASSp
11/01 ASSp
1/03 *Motel 6 & ASSp & PAP#3
11/03 Pop Century planned
* off site