> We may still have all the information, but no one will be able to read it except maybe ancient history professors. At the rate language is changing, the English we use today will be exceedingly obfuscated in 50,000 years. It'll be like watching today's 16 year olds trying to read Chaucer or something even older, but magnified. It took a long time for the English language to invent spaces between words. I can't even imagine what new reading processes humanity will have in 50,000 years. That is, if we're even able to read at all. I see it working two ways. The first, letters forming words are obsolete, and there is a single symbol for almost any word you may want to say, even a single symbol for entire sentences. We have no letters, just a myriad of symbols that are impossible to interpret from an outside perspective. (Darmok and Jilad at Tanagra, anyone?) OR, our alphabet will expand. Words will be made of fewer letters, but we'll have more to choose from. Instead of 26 letters, with various accents and whatnot, we'll have 100 or more.
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> -relishgargler

Quite apart from what gremlinn said, languages simply don't change in those ways. In the last 3,000 years, only four letters have been added to the ancestors of English, and no alphabetic language has ever added new letters (or lost old ones) since the printing press was invented; indeed, the tendency has been towards standardisation and codification. Admittedly, you can point to a current trend to use numbers in place of letter sequences, and novel abbreviations, but this is a (probably transitory) result of small, multi-tap keyboards being common; once better input systems for portable devices are developed, I'd expect those trends to reverse.

Letters rather more commonly gain accents, or shift their phonetic value.

The other thing you mention is English switching from an alphabetic to a logographic system, with one symbol per word or sentence; such shifts are unprecedented, and if by some miracle it did happen, there would be no way we would ever call the resulting language "English", any more than we call our current language "Phoenician". And logographic languages are even more resistant to change than alphabetic languages; Chinese documents written 3,000 years ago can be trivially read by schoolchildren. New symbols have been added for new concepts and technologies, but the old symbols remain unchanged in both form and meaning.

Far more likely than that the English language will be unrecognisable is that it will have died out, to be replaced with an unrelated (possibly artificial) language. My guess is that in 50,000 years, English (or its descendants) will be more similar to Modern English than Modern English is to Latin, simply because of the massive stabilising effect that technology has on communications.