Wishful thinking, but unlikely. Downwardly mobile societies usually turn to fascism to stop their decline, rather than going back to their democratic liberal roots.
I think he makes a very interesting argument and I already ordered the book. A few observations.
1. The predictions of the downfall of the Soviet Empire are nothing new, all right. But the ones who first saw it coming were Soviet dissidents. I recall a samizdat by Soviet dissident (his name escapes me at the moment) titled "Will the Soviet Union Survive until the year 2000?" circulating in Eastern Europe in the 1970s. The answer was no and for the reason cited in this review - internal economic inefficiencies (well know to central planners since the 1950s), bloated military, parasitic oligarchies, moral bankruptcy of the system.
Those prediction came true. The author also predicted the rise of fascist tendencies in Eastern Europe after the collapse, which were marked - especially at the grassroots level but not dominant. I think what prevented this grassroots fascism from becoming a full blown version was the kleptocratic privatisation - the ruling class could gain by stealing state property without the need of fighting organized labor (as I was the case of Italy or Germany) - so all they needed was Thatcherite laissez faire rather than fascism.
2. A lot of his observations about the parasitic nature of the US state and society is true, but that does not necessarily translate to a collapse. Al elites are by definition parasitic to some extent, i.e. living off resources produced by others, but that parasitic nature is tolerated as long as the producers get something in return. That "something" is usually - to use Hobbesian imagery - the cessation of war of all against all. The Leviathan may be a parasite, but as long as he maintain the peace and the established order of things, everyone consents to his rule.
I think it was what kept the Soviet empire in place - in the later days of the empire, Moscow had little power over the regions, and maintained its position mainly by federal subsidies and by keeping peace among conflicting regional interests. The empire collapse only after Moscow under Gorbachev abrogated its Leviathan role.
That seems to suggest that even internally corrupt empires ruled by impotent elites may have longer shelf life than Todd seems to suggest, unless they "drop power on the floor" by themselves. I think that the Bush and Rumsfeld gang understands that very well and tries everything in their power not to drop the power.
3. The adjustment of the wasteful US life style to live within its means is certainly long overdue and most likely already in the pipes. However, this adjustment will most likely take the form of significant but gradual price and cost of living increase, cuts in public services, stagnant wages etc. i.e. business as usual, only more of it. The most likely outcome of that adjustment is the rise of religiosity and popular fascism which will not escalate into a full blown form, since the elite has nothing to gain from it. Radical change? It simply will not happen here.
Wojtek