no, it's not a fork.
I don't really agree, but this is mostly a quibble about terminology and what is meant by a "fork", so it's probably not worth pursuing.
In the very unlikely event that there was an unrelenting 51% attack that rendered the bitcoin network unuseable, would you prefer migrate to a network that uses the current blockchain, or a network that uses a copy that is 1 year old?
I believe the economic majority would migrate to a new network built from the most accurate and current version of the blockchain of the coin with the largest market cap.
Here I am nit-picking at a rather minor element of the proposal, so this may also not be worth pursuing. (But it's more substantive than terminology.)
Do you mean
from the largest market cap, or
to the largest market cap? The latter makes more sense to me. For fairness I'd prefer the network based on the most recent known good block-chain, and for greed I'd prefer the network that gave my coins the largest real-world value. If there were two candidate alt-coins, and one launched just before I bought a house and one after, then I might prefer the older one because it would give me more coins.
I do think a block-chain that is years old is probably not recent enough.
if aethereum lasted that long it would have proven itself as a viable cryptocurrency contributor, which is what we all want.
Well, merely "lasting" doesn't mean that, but if it is the most successful alt-coin then presumably it would be.
I'm not yet sure I do want aethereum to be a viable crypto-currency. I'm still thinking about it.