Is it time for an EF-6 tornado classification?

In recent years, there have been arguments for an EF-6 tornado classification for these extreme tornadoes with winds measured by doppler of around 300 mph.

The Wright-Weather blog has an interesting update on the amount of damage related to the increase in wind speed.....click  HERE    This comes up after the near 300 mph wind speed measured with the El Reno tornado in Oklahoma. 

If you look at the EF chart below, you will see that each category covers up to a 35 mph difference and then everything above 200 mph is rated as an EF5.  There is some evidence to show that there are lower end EF-5's which are devastating and an upper end  EF-5 which is even more devastating if that is possible and it seems to be.
One thing to remember, these reports of 298 mph winds are coming out from the El Reno tornado. This is not at ground level. In most cases, the measurements come from several hundred to several thousand feet above the ground.  In the follow-up NWS storm surveys, the wind speeds are based on the type of damage done at ground level.  There has not been an estimate of 300 mph winds from a tornado at ground level.

Also....here is another interesting blog from one of my weather favorites, Mike Smith, out of Wichita. The article talks about KFOR in Oklahoma City telling people to drive south away from the city during the tornado warning and that if you were not in an underground shelter, you were going to die.....click  HERE