Personally I think the progress of knowledge will only accelerate. Progress of knowledge with us mortal depends on some one person to take the combined work of his predecessors, maybe add some work of his own, and fuse it in to some brand new understanding of something. Pick any great scientist in history, if it wasn't for all the other scientists before him, he would still be struggling to light a fire outside his cave. But transferring knowledge from one living being to another is difficult, time consuming (Takes us a minimum of 16 years to get any half-decent amount of knowledge), and inevitably many details get lost in the process. But if one human were to be allowed to carry on his research indefinitely, then eventually all the previous knowledge he will have to rely on will be first-person, which is much more detailed and accessible. No scientists will ever die in the middle of research, and no other scientists will have to spend time piecing together what he did leave behind.

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After you take away everything that is impossible, whatever is left, no matter how improbable, must be the truth. ~Sir Arthur Conan Doyle/Sherlock Holmes