Phil makes some good points about future-proofing his community (make sure you're subscribed to his blog).
The problem is future-proofing a community is different from future-proofing a community platform.
There is one way to future-proof your community, disentangle the community from the website. The platform shouldn't house the community, it should be the place where the community often to chat. The platform is to an online community what a village hall is to your local community. It's important, but the community should be able to survive without it.
Create bonds that aren't platform reliant. Facilitate connections between members on Facebook, Twitter and e-mail. Foster a swirling mass of connections between members online and offline of which the platofrm is one element amongst many.
It's difficult to control, but community management isn't about control, it's about facilitation and support.