Well, it's arrived, and you can download the 'Summary for policymakers' here:
The key diagram is on the last page, p21. This shows the predicted evolution of global temperature over the course of the 21st century, for the six SRES 'marker' scenarios. By taking an average over the output of the various different global climate models, each differently coloured line represents the predicted evolution of global temperature under a particular scenario. Scenarios prefixed with an 'A' are scenarios in which economics are the driving factors, whereas scenarios prefixed with a 'B' are scenarios in which environmental policies are the driving factors. A1FI is the scenario in which fossil fuels continue to dominate global energy consumption, A1B is the scenario in which fossil fuels reach a balance with renewable energy sources, and A1T is the scenario in which there is a transition between fossil fuel usage and renewable energy.
The cost of solar energy is halving each decade, and solar energy is predicted to become a competitive rival to fossil fuel circa 2030-2040. Accordingly, the A1T scenario used in the third IPCC assessment report in 2001 represented CO2 emissions to decline beyond 2040. Assuming that economics will continue to be the driving factor, the two most realistic scenarios are therefore A1T and A1B. The scenario which produces the highest estimated rise in global temperatures, the A1FI scenario, is technologically and economically unrealistic, so the upper limits of the IPCC temperature range can be discarded.
The predicted temperature change under the A1T scenario averages out at 2.4 degrees C, with the various climate models producing a range of predictions between 1.4 and 3.8 degrees C. The predicted temperature change under the A1B scenario averages out at 2.8 degrees C, with the various climate models producing a range of predictions between 1.7 and 4.4 degrees C. In both cases the uncertainty is of the same order as the 'most likely' temperature change. There is still an awful lot of 'noise' being produced by the global climate models.