The current JIR has a good piece on Iraq's near-term outlook titled: Losing Ground: The Future of Central Government in Iraq. It consists of a situation summary, and then, using their country risk modelling methodology, they lay out three potential scenarios for '07. Scenarios one (Unitary Iraq) and three (Government Collapse) they rate as low on the probability scale, with scenario two (De-Facto Partition) being most likely.
...the government is highly unlikely to regain a monopoly of violence in 2007 no matter how successful its development of the Iraqi Army. The key dynamics are not between the government and the militias or the insurgents, but arguably between the various armed sub-state groups themselves. The multinational presence will slowly draw down in 2007, but not significantly enough to end the sense of an occupation. Instead, the key effect of withdrawal is likely to be to exacerbate sectarian and factional grievances that have been restrained to a degree since 2003...
If you can get access to a copy of JIR, it makes for an interesting read.