May be you don't agree, but facts are against your idea.
I want to give you some data (not opinions) about all my athletes able running under 27' :
Nicholas Kemboi (26'30"03) able to finish last 600m in Bruxelles 2003 in 1'23", almost beating Haile (26'29"87), could run in about 51"5
Ahmed Hassan (26'38" in the same race) NEVER could run faster than 53"5 / 54"
Imane Merga (26'48" this year) able to finish in 53"5 in 5000m last year, can run 400m near 51", not faster
Moses Mosop (26'49") finished last lap in WCh 2005 (bronze medal) faster than Kenenisa and Sileshi (53"4 for him, but was only 5th at the bell). He NEVER can run near 52"
John Korir (26'52") had a speed not better than 54"
Mark Bett (26'52") could run about 51"
Wilson Kiprop (last year winning Kenyan Champs in altitude in 27'26" and the African Champs in 27'32" woth last lap in 55"6, that could easy run under 27' at sea level) became the WCh of HM and NEVER could run under 53"
Now, after Cova, I can tell you that nor Antibo (European Champion of 5000 / 10000 in 1990, and silver medal in 10000 in OG 1988), very fast in the last lap, neither Panetta (27'24" and WCh of 3000 steeple in 1987) could run UNDER 52" (and Antibo was one of the fastest sprinters in the last lap).
When we speak about ladies, we remember last 400m of Defar and Dibaba in the IAAF final of some year ago (56"5 / 56"6). How much do you think was their potentiality in a 400m race ? Not better than 54"5.
Try to understand that a Dibaba able running 53" can easy run the WR of 1500m. Wang Jungxia ran 3'51"9 in 1500m and 2:24 in Marathon, and 8'06" in 3000, and 29'30" with the second half in 14'26", and NEVER could run 400m faster than 55"5 (this was what Dong Li, the WCh in 1500 in 1997, now wife of the head coach of Spain Miguel Landa, explained me when we spoke about the Chinese period of Ma Juren).
This is also the answer for the other poster speaking about the relation between 400m and 10000m (75% of the speed) :
THERE IS NO RELATION BECAUSE THE TWO SPEEDS ARE PRODUCTS OF DIFFERENT PHYSIOLOGICAL SYSTEMS (the first Mechanical / and Lactic System at 90%, the second Aerobic System at 90%, including in this percentage also the lactic resistance, that is connected with the Aerobic System more than with the lactic system).
Try to understand one thing : IF YOU ARE ABLE RUNNING FAST 400 m IS BECAUSE YOU HAVE A HIGH PERCENTAGE OF FAST FIBERS.
IF YOU HAVE A HIGH PERCENTAGE OF FAST FIBERS, NEVER YOU CAN HAVE A HIGH PERCENTAGE OF SLOW FIBERS, SO NEVER YOU CAN BE TALENTED FOR RUNNING LONG DISTANCES.
If a medium level athlete (30' in 10000m) runs 3 km in 10' together with Asafa Powell (supposing Asafa can be able to do it) and after they can have a last 400m free, in a race of 3400m, THE WINNER IS THE SPECIALIST OF 10000m, NOT ASAFA.
Of course, probably is for that over-estimation of the effect of speed that is so difficult to have TODAY in our Countries (from Europe to US) strong specialists in long distances, in any case very far from our specialists of 25-30 years ago (so, don't look at Africans, but at European or American of the period 1970/1990).