I'm not sure what you mean by file formats becoming obsolete all the time. This may be true for some proprietary formats that are no longer readable by a modern application, but for any reasonably widespread format there should not be much difficultly. I don't see any reason why we wouldn't be able to read most of our text, image, and video data decades down the road.
Remember, we're supposedly entering the "post-PC" world. How do you intend to open a WordStar document or Quattro in 2040, after 30 years of app stores and sandboxed apps?
The presentation of documents are critical as well. Will complex documents created in Word 95 render properly on the iPad XXXVI in 2040?
Archival file formats like PDF/A, open specification formats like OOXML and open source formats like ODF will help with this issue, but I'm sure there will be many audio and video files that will be unintelligible in 30 years.
