Trust me, the internet is never going down (permanently). There might be some minor disruptions, but the world is beyond interconnected at this point.
Yes its never going to happen especially that internet is very important on each country since to many things will be lost if this incident will happen so for sure government also avoid to make this incident to happen.
But if there is a political crisis like civil war or anything related to that situations or also natural phenomenon like solar storm which has been tackled up since it can disrupt the internet and other services this incident will happen.
Although those things is far to happen especially that we are now in modern ages and anything issue provably can be avoided. But one thing is for sure there bitcoin will remain, but for its value if those cases happen I guess that is the questionable matter.