What? I get the 26.30 bit. My 8m/second observation is an application of typical max speed for a marathon runner now and in the future. Don't say "only 25 seconds for 200m" That's plenty fast enough at the end of a race. Can you sprint flat out at the end of a 25 lap race?
But lets stick with 8m/second, because it's realistic. It is also realistic to expect that in future, such a runner will be able to hold 6m/second for 26.2 miles, because what we are really discussing is the ability to use eccentric muscle contractions more and more, which saves energy and makes a faster race more economical. And that in a nutshell is what World Records are all about.
All of the typical discussions here involve lots of posters with no real knowledge of ex phys (but think they are experts)spouting off about this and that and ignoring what it is in every runner that makes you float along easily at a rapid pace, when you are running well.