Typically, it's not the threads that are seized. There is a sleeve that the axle bolt runs through. The sleeve is in between the inner bearing race of the two front wheel bearings. The bolt seizes along the length of this spacer. Of course, if the bolt won't turn at all it could be seized in the thread, but once that is loose, the spacer tube will be your next obstacle.
Another (crazy, but doable) option is to drop the fork tubes out of the triple. Then, assuming the bolt is seized on both sides you can turn the fork tubes against each other. One side will have to break free. Best case scenario is that it is the threaded side. Then with that fork off of the axle, you can try getting the wheel off of the axle. If the spacer tube is seized to the bolt, this will involve knocking out the balls from the front bearings to separate the inner and outer races. Then the wheel/tire can come off and you can focus on getting the rest of the stuff unstuck.
This is not a fun job...
- Frank
1984 200ES Big Red
1985 350X (x2)
1986 350X
1986 250SX
1984 Auto-X
1984 ATC70
1985 ATC70