Your Solidity contracts can run on Ethereum Classic, which you can be confident won't be forked since its users tend to believe in the principle of the immutability of the code.
If I'm going to trust the enforceability of my contract to some group of people, I trust the established legal system--warts and all--much more than the mob rule of the Ethereum crowd.
If a fork happened in Classic to protect some party's financial interests, I think the more likely scenario is the great majority of miners opting to stay on the original branch.
I get that it's not a complete guarantee, but neither is the legal system. Contracts can be invalidated based on a judge's perception of their unfairness, on a technicality, or even on a whim.
Also known as "miner consensus", same for all crypto currencies including btc
So is bitcoin.
Unless they're interested for purely speculative purposes, in which case it was a good bet that the non-Classic version would be more remunerative.