Come back, no chance. Additionally, you have to consider a good chunk of the 100k online at all times was bots, autobuyers, and other crazy shit like that, to the point where people used to run multithreaded autobuyers using 20 different accounts to refresh.
While I agree neo is dying, it is more due to the fact that 1) people no longer spend all day on neo like they used to. People think that games has age groups, I consider it that games have generations. Our generation, most of the neo players, are all pretty much young adults now. That being said, if we're not busy, we're playing MMO's, shooters, or overall getting the lights boozed out of us.
Without advertising or fun things such as plot points, wars, etc. the game will never make a comeback. This was a calculated move for neopets, as it realized it was reaching the end of it's life so it went from an "expansion" marketing model to a "cash cow" marketing model, where they try to milk as much money as they can before the game crashes to it's low. I doubt it will ever completely die off though.