Running out of "Steam"?

[KillerDraco]

Because as people migrate to the new games, there's no point to continuing to play the old ones? Particularly as that migration often involves moving Pokémon ahead, a one-way journey that leaves one's older games barren of anything worth battling with.

This pretty much hits the nail on the head. Speaking from personal experience, every Pokemon of worth that I've ever caught has been moved to Gen V, since it's the most current and up to date. Nowadays, the only thing I use past gen games for are special runs (Nuzlocke, Monotype, etc.), or if I need another Legendary from that version. But when the bulk of the battling/tournaments are done exclusively for 5th Gen, as are the giveaway events, there's little point in investing too much time into Gen IV or anything prior.

[Zenotwapal]

they use the same idea over & over again for pokemon.. and yes something can be over used but the terms "over used" are different for everybody.

Also back on topic: Why would everyone stop posting just because new games are out?

As BCVM22 has stated, people move onto the newer games. These sections are never posted in because peopel rarely play the older games when they have the new ones.

[Dragon35]

It's odd how everyone plays Gen V because it is the current one, loads will play Gen III for a challenge (Scramble, Nuzlocke etc.) which squeezes out Gen IV leaving it alone and empty

[KillerDraco]

It's odd how everyone plays Gen V because it is the current one, loads will play Gen III for a challenge (Scramble, Nuzlocke etc.) which squeezes out Gen IV leaving it alone and empty

Meh, I find Gen III a little overrated to be honest. I personally prefer Gen IV for its superior balance (more types have usable moves, the physical/special distinction), so Heart Gold and Platinum make for good special runs imo.