Eh, I don't think that's the best analogy. The lumber industry largely collapsed because they were harvesting a finite, non-renewable resource. Honestly there aren't many lumber mills owned by big business anymore - the few left in our area are all locally owned actually. There were definitely some shady corporations that helped tank the industry but that was not the only factor. There just isn't much left to be logged anymore, and what is left is either very difficult to log due to terrain or of poor quality. Really, the logging industry really has no one to blame but themselves and their own short-sightedness. The same will be true of most growers - this has been coming for a long time and you would have to be blind not to see it.
If it goes legal this year, some people will definitely be hurt economically. However, it will also present a tremendous amount of new opportunities as well. There will always be a niche for craft products - but you need to be willing to work hard, and produce a superior or unique product. The best wine is made by place like Opus One, not Carlo Rossi, the best brandy is made by places like Germain Robin, not Christan Brothers, the best beer is made by place like North Coast Brewing Co, not Anheusier-Bush. The same will be true with cannabis - those with the passion, the dedication, and the artisinal touch will thrive despite the involvement of big business. Hate to sat it but there are a lot of REALLY shitty growers in NorCal who don't give a rat's ass about anything but they money - those will be the growers going out of business.
Personally, I am excited about the prospect of legalization. I would LOVE to be able to do what I do openly and freely and not have to worry about legal ramifications. The though of being able to turn growing into a real 9-5 job sounds absolutely awesome to me - even if that means having to work harder and make less.