Will all knowledge found on internet be available forever ? (barring worldwide cataclysms). I understand that academic and governmental institutions may maintain their sites, but what if Google, a private institution who intends to put X millions of books on internet, will go the Panam way ?
Maybe, Somewheres, Sometimes, Someshow, Someones will squirrel it away to be found again in the far distant aftertime.
The only thing consistent about change is that it too changes. 
This is probably for another forum because there are few factual answers about what will happen at indefinite points in the future. But I don’t think Google, to pursue your example, keeps every page it indexes forever. I don’t know this for a fact, but it is a search service, not an archival service, so its primary mission is to allow you to find pages that are currently available on the Internet.
First, not all information is necessarily desired to keep around forever. (I try to convince Mrs. Gas of this every time I open the box in the basement that has credit card receipts and utility bills from 1983.) Even the IRS only keeps data for around 75 years.
Second, we are already seeing examples of digitally archived data the retrieval of which is threatened due to changing technology–I have a pile of 5.25" floppies but no drive to read them with anymore, and the drives are getting scarce. That’s just a quick example; there are other tape and disk formats that have been used industrially and not by the general public that have also become obsolete.
There is no central entity that gathers and archives all the information on the Internet, so I would say that not all knowledge found today on the Internet will even be available next week.
No, information on the Internet is notoriously transient. I’m sure you’ve encountered your share of 404 - Page Not Found errors. This isn’t even a question about the future; stuff is disappearing from the Net all the time already. If you want to keep something, make sure you download it yourself and save it to a backup device or print it out.
The closest thing I know to a public archive of the Internet is the Internet Archive’s Wayback Machine, which lets you view past versions of archived webpages. It’s a great service, but of course it can’t archive every single page on the web – or even most.
Well, the PanAm corporation went away, but not all the assets.
- the pilots flying for PanAm found jobs with other airlines, and continued to use the training they got from PanAm. Same for mechanics, stewardesses, etc.
- the planes being flown by PanAm were sold to other airlines, repainted, and continued to be flown.
- the big PanAm building in NYC was sold, renamed, and continues to be used.
- all the PanAm gates at various airports were sold or re-leased to other airlines.
- even such mundane items such as the supplies of PanAm stationary were sold off and used up by somebody. (Some of the logo items like uniforms, flight bags, etc. now command absurdly high prices as ‘collectibles’.)
Generally, anytime a private company goes bankrupt, all the assets are sold, and used by somebody. In the case of Google, that info is a major part of the assets. The creditors would certainly demand that the bankrupcy judge force a sale of them. So somebody would get them – they don’t just disappear.
But some assets become useless over time. Will lots of 9-track tape archives be of use to anyone without machines and OSs to read them? Archived data is overwritten for space, shredded or wiped, disk drives cost money to keep spinning, hardware takes up space and can be sold/scrapped/rehabed to other purposes.
Info is already lost and more is being lost each day. Granted, far more “stuff” is being created to take its place, but how do you determine today which is the valuable stuff and which is transient junk?