Sure, those old passes never expire.
You will not be doing an "upgrade" or a "trade-in" for a different type of ticket. But the tickets from 1988-89 pre-date the current type of tickets with magnetic strips, so they won't work in the turnstiles. You will have to exchange the old media for new media (i.e. new cards with magnetic strips). You can do this at any ticket window or Guest Relations window at the 4 theme parks.
When you exchange your passes, ask if you can keep the old ones as souveniers. They will have to be stamped VOID first, but hopefully you will be able to keep them, since they are a nice memento of an old trip.
You might also carry a pen to write down how many days each of your new tickets have left on them, since the new magnetic strip media don't get stamped or punched when you use a day.
The new magnetic strip media also have a huge advantage over the older tickets - if you have the serial number of a ticket, Disney can replace it for you if you lose it, just like losing your ATM card. The lost one can be cancelled out of the system, and you can be issued a replacement. Just write down the serial numbers of your passes, which are printed on the back, and keep the numbers separate from the tickets.
