Timothy Burke writes that Zimbabwe's future is really grim, no matter what:
Obsidian Wings: Zimbabwe Melts Down: Much as I think Mugabe is loathsome, and that his loathsomeness was consistently underestimated by many observers and commenters of Zimbabwe's politics in the 1980s, it's important not to overlook the more systemic problems in the postcolonial Zimbabwean state. Mugabe is not in fact a charismatic authoritarian who somehow overwhelmed an otherwise competent or well-functioning liberal democracy and drove into ruin. He's certainly an autocratic and unscrupulous control freak, and has been ever since he first entered politics. But what has happened to Zimbabwe since the late 1980s has as much to do with a wider circle of people around Mugabe, both in the ruling party and in important and powerful institutions, including the military.
When Mugabe dies, I wouldn't expect things to get magically better. First, because much of what gave Zimbabwe a promising economic and social outlook circa 1988 has been thoroughly and structurally destroyed. Second, because at least some of the people around Mugabe have instincts just as self-destructive and have every reason to inhibit good management or democratization (as they will likely be the ones prosecuted by a vengeful reformist regime).
The problem with fantasizing about unilateral military action in this case is connected to this problem. You could drop a bunch of Special Forces guys on the presidential palace in Harare, take out Mugabe, and change absolutely zero. Frankly you could occupy the country with UN forces and change absolutely zero. What's needed is a huge change in the fundamental architecture of the Zimbabwean state and a change in the basic composition of the thin upper range of the most powerful elite. Those are not transformations which occupiers can readily bring about (something which I'd think should be screamingly apparent to everyone by now).
About the only positive short-term scenario is that some of the younger, smarter, more competent guys in ZANU-PF who have been carefully keeping their heads low through the last decade will move aggressively on Mugabe's death to push aside hacks like Didymus Mutasa and clean out the bureaucratic house. But to really succeed at that, they'd have to reverse a lot of brain-drain and draw back competent managerial and professional elites who have (wisely) left for other countries.