Do you box things up for them to have later and stash things away in the attic. Do you kick it to the curb or the donation box? In my own home many things were kept while items myself or my children someday wouldn't have interest in were donated.
Mom always made it a big deal to send the entire set of something to other boys and girls who might like it. I always felt like I was giving another child a huge gift because my own personal emotions were so entwined, even though I didn't really want to play with things anymore. Many friends however have parent's attics stuffed with their youth.
How do you plan on handling this? Have you been confronted with it yet? First things first, make sure to notify all relatives of the change so you don't end up with a sea of Spongebob at your next birthday party when they've already moved on to Playmobil.