Each time, google attacked on seo community using 1 animal (panda) and 2 birds (penguin, humming bird) to announced their major changes in search.

Now a days, with the evolving technology, the devices at our disposal are becoming more and more sophisticated and hence our ability to interact with them are becoming more and more advanced. Keepin this in view, I believe that these changes are for better and a much evolve search.

With the advent of Humming bird the targeting changes drastically, we now have to be more intent based i.e, targeting is becoming more precise. Moreover the animal (panda)  and bird (penguin)  of google is making us pay more attention to the quality.

So  it spells out as thus, quality and precise. And don't we all want this :)

Interesting question. Really depends on the SEO professional that did the early work... Let me explain:

These updates are based on Google Webmaster Guidlines that have somewhat remained unchanged. If the SEO Professional did the right and understood his/her limits at the time you will not need to worry much at all. Unfortunately, white hat well skilled SEO Professionals with real experience are hard to catch. Reading a few blogs is simply not enough to make anyone a SEO genius. The key is the do a proper keyword research and naturally build a theme that relates to your audience. It is not about buying links/spaamming off page, or keyword stuffing on page SEO.

Hope I made sense.

It will defiantly do some damage but if you think about it, it will help smaller websites and even people who don't work on their SEO without them knowing ! 

@Salah G Hamed

Actually Google Search is no more a Search Engine. Google become a corporation who always think about their inversters or a stakeholder. They are not going to think about smaller websites :) actualy they are behind some big cash fish.