I would predict toys become collectible roughly 20-30 years after their heyday. Ie when the kids have grown up and want to relive their childhood.

So that would make pogs due imminently.

Mistakes (on coins and stamps) is a reliable indicator, actually my dad has a blue thunderbird 2. Most tvs were black and white, so they didn't know what the colour was, or didn't think it mattered.

Then you have the famous flops. That ET Atari cart is probably quite valuable, same for the Sinclair C1.