Take it with a grain of salt, but a leak from earlier this month indicates DG1 may not be much more powerful than the integrated graphic that will be used by Intel's Tiger Lake processors.
The latest leak from EEC points towards 96 Execution Units. If Intel was to keep the same design principle for DG1 as for Intel mobile HD/UHD graphics, then we should expect 96*8 shading units, that’s 768 in total. It is pointless to speculate if this is 768 or 1536 (*16) shading units, but it appears that DG1 focuses on entry-level graphics. Intel’s Tiger Lake is also believed to have 96EUs (featuring Gen12 Xe based graphics).