Interesting bike, but not available just yet.
I have been riding motorcycles for 40 years both on and off road, and I actually write motorcycle travel books for the southwestern U.S. (shameless plug) [url=http://www.southwestmotorcyclerides.com] is my web site. I have ridden over 500K miles on bikes. More of that riding has been road riding on Harleys, but I have also had many dual sport bikes, which is what you want if you are looking at a bike.
Let me suggest two good ones: 1) Kawasaki KLR 650 is a very good dual sport and has a 6.5 gallon gas tank for great range and 2) a BMW Paris-Dakar dual sport. These are no longer in production, but you can find some around. they have a 9.5 gallon gas tank for extreme range, but they are somewhat top heavy and I call them a pregnant waterbuffalo, but they are a good bike.
Having said that, I would agree with others that an ATV is better for bugging out of clogged cities. You are much more stable, can carry MUCH more (including gas) and the newer EFI ones are getting better gas mileage all the time. The Suzuki KingQuad has a 4.6 gallon tank and gets (your mileage may vary) 20-25 mpg so about 100miles just with one tank, maybe more if you are very sparing in how you ride. With 5 more gallons you can get 200+ miles, not bad if you are trying to escape a storm. My .02.