On April 1st 2003, when SARS was in full swing, the WHO reported 1622 cases and 58 deaths. That is a rate of 3.5%. In June 2003 (at the end of the SARS outbreak) the official figure was almost ten percent. From this comparison you can expect the mortality rate of the new corona virus to be at around 6 to 8%.
It is dangerous to extrapolate like this because the big differences are in incubation time and the fact that the novel coronavirus is likely spreadable before the carrier has a fever or other detectable sign. If that's the case, tracking the spread might as well be impossible because multiple people could be the potential source without a clear way to trace it, especially in a hospital setting.
On the flip side, the R0 (rate of transmission) and death rate might be a good clip lower than currently estimated. On the other hand, China walled off a city but part of their motivation might have been the flack they got for moving slowly with SARS.
Source: https://www.who.int/csr/sars/press2003_04_01/en/ (search for "deaths")