For what it's worth, I've pretty much been surviving in this sector for a decade now off of a large chunk of organic traffic and quite well too. And for 10 years people have been rolling out the same tired warnings of relying too much on organic traffic. The warnings haven't stopped me and I have no regrets, because it's been a rather good run. Sure, I'd rather have a more diverse range of income. But if it's working well, you stick with it. You don't turn down a good thing to be more balanced. And I have enough development skills to get a 9-5 job if I really needed it. So it's not nearly as risky as people make it out to be either.
Back to the original topic.
This encroaching on results is not really the end of the world. I rather doubt it will have nearly as major an effect as Google would like it to have.
The big threat for sites relying on organic Google traffic is not Google inching in on results. It's Google losing relevance while those travel specific players gain more and more market share (ie Kayak, Tripadvisor). Already, as tedster's comment suggests, a very large percentage of people never will search through Google for this kind of thing because there are currently better alternatives. If Google loses too many travel searches to those sites, then that means all the sites appearing in organic results also lose. And If there does end up being only 1 or 2 definitive travel sites to do all the travel searches on, then there won't be a way for other sites to get a slice like we have been able to on Google.
Unfortunately GHF is not really all that fantastic. We'll have to wait and see how this all pans out I guess.