You can't use any WDW tickets - old or new - for admission to WDW. WDW and DL have entirely separate admission.
You can't use any WDW tickets - old or new - for admission to DL. (Sorry for any confusion that caused!)
This is incorrect. If the tickets do not have an expiration date on them, yes, you can use them. Here is a clip from Mousesavers.com:
Interesting, unpublished fact: you can use any unexpired, leftover days on a Walt Disney World ticket at Disneyland or DCA! Present the Disney World ticket at the gate on arrival -- they will take it somewhere, deduct a day from it, and give you a one-day Disneyland and/or DCA ticket.You can repeat this day by day until the Disney World ticket is used up. They will not give you a multi-day ticket all at once, even if you have multiple days left on your Disney World ticket.
The type of Disneyland ticket you will receive is based on the Walt Disney World ticket you present: if you have a Disney World ticket with the Hopper option, you will get a Disneyland Hopper that allows you to visit both parks in the same day; on the other hand, if the Disney World ticket had no Hopper option, you will get a one-day/one-park ticket and will have to pick which park to enter that day. This has been going on for at least 5 years that I know of, and the information was last reconfirmed by a MouseSavers.com reader as of May 2007.
Disneyland passes are NOT accepted at Walt Disney World, and Annual Passes are only good at the park where they were purchased (WDW Annual Passes are NOT good at Disneyland, and vice versa)."