Don't worry. According to Mike Hearn Bitcoin can survive just fine with 4 or 6 (forgot which) copies of the blockchain worldwide.
Is he right or wrong about that?
Via what methodology would we test that hypothesis before arriving at a conclusion about its validity?
Who cares? Before you ask that question you need to show reasonable likelihood that increasing the block size to 8MB will drop the number of full nodes to 4 or 6.
Frankly, I think that a dramatic reduction of nodes is more likely if Bitcoin becomes a settlement network than if the block size is increased to 8MB. NOBODY will be interested in holding the data if they can't use the network, so the only full nodes will be those sponsored by the payment aggregators. These aggregators are also perfect locations for governments to apply identity and green address pressure, destroying fungibility.
i'd agree with this. altho i'd like to see the block cap removed altogether, certainly i'd go with Gavin's 8MB BIP101 proposal short term to ease into the long term goal. i'm sure this interim solution would make many more ppl happy.