I really hope PC lasts a long time, even when I've moved on. As for strategies to keep PC afloat, I am not sure. Other members (namely @Nihilego) are demonstrating that ROM hacks are the bread and butter of PC, and personally, I have had little interest in those sections of the forums; however, if this is true, PC should focus its efforts on that section because without that section, the rest of the forum that we love and enjoy may fall to pieces.
Personally, I think it also really comes down to how much longer the Pokemon franchise and Gamefreak will continue to produce Pokemon games. The Pokemon discussion forums are significantly more active than the past generation forums from my experience.