Ok my bad, but the Junta is doing pretty poorly. At this rate Mandalay will fall this year.
It's true they have definitely been doing poorly, but I would hesitate to extrapolate their failures going forward. Look at the topography:
Shan sits entirely on a plateau with lots of hills, but once you get to Mandalay the terrain drops off into river valleys. Rugged hills are great for light infantry, which is most of the ethnic forces. But the open ground favors heavier artilllery and airpower, where the military holds the edge. Also the ethnic groups are native to Shan, so they are fighting on familiar ground. But the cities are Bamar-dominated, and not all of the civilians there hate the military (many do, but not all). And they will definitely hate being ruled by minorities.
I agree that things are looking pretty bad for the junta, but I think the rebels will struggle to close it out. They might not even try; the ethnic groups know they probably can't hold onto the cities even if they win (have to give them to the Bamar NUG), so how motivated will they be to fight for them? My guess is that individual provinces will break into mostly autonomous chunks like warlordism. Nobody is strong enough and unified enough to control the whole country.