Mr. Freeze,
That would be a good guess, but what you're seeing in the video is the fuel manifold rupturing. The fire in the video is insignificant, and isn't the cause of the separation.
It's a valid assumption, however, in that we thought that was what happened to T82 years ago. It had been flying straight and level on a load and return, empty, south of Palmdale, CA. Whitnesses saw an explosion, followed by a couple of secondaries, and the wings separated.
At the time, and what has been taught in groundschools since then, was that a wire short from a fuel quantity indicator caused an explosion in a drybay (interior service area in the wing between tanks). It was believed that the circuit breaker had popped, and that the FE reset it. It was believed that it popped again, and that the FE reset it again, triggering the explosion.
Some validity to this belief was provided because this happened to several of the same type, on the ground over the years, and personal accounts verified the cause. However, in the case of T82, no such verification was available, because like T130, everyone who could verify the problem was dead.
Only in the past few years has the information applicable to this incident, and T82, been known. Presently, all the A models are grounded pending further investigation. As stated before, the crews and those operating the aircraft know what happened, but speculation right now will only serve to cause potential damage to the air tanker program, and won't generate any useful information outside the industry. It's very much an in-house issue.
Steve Waas was one of the most experienced tanker pilots flying. The memorial for all three crewmembers was Saturday in Minden, NV. T-00 (A P-3A) did a flyby and turned west, symbolic of Tanker 130 flying west.
Mike Lynn, a giant of a man and a staple in the tanker industry, has posted a web tribute to Steve and T130, for anybody who might be interested. Mike was Steve's best friend. I'll get the link and copy it here for those who might wish to visit it. It won't provide any dirt on the crash, but is a nice reflection on the man who flew the airplane.