I have though of the main possibility of bitcoin collapsing [...] if all the goverments will start making bitcoin illegal.
what are the chances for that to happen
If major governments were to decide to make a concerted effort to oppose bitcoin, I think they could pose a major impediment to large scale adoption. First, it would be difficult to convert between fiat and bitcoin. Second, bitcoin would not be adopted by large scale businesses like amazon, making bitcoin less useful to Joe on the street.
The most important question is whether governments (or the rich people who influence government, in the case of the US) will be motivated to oppose bitcoin, when they could embrace it / harness it for their own purposes.
If you are a wealthy banker (who is knowledgeable about bitcoin), for instance, you might decide to invest in bitcoin rather than influence government to oppose it.