Last year in September they’ve done a loyalty promotion for NP1 and NP2 users and offered a pretty good discount on the NP3. You didn’t even have to send in the device, so you could actually sell it yourself and still save money on the NP3.
As for their own trade-in deals, these have been requested a number of times in the last two or three years, Nothing mentioned they are looking into it, but no specifics were given.