http://www.easy68k.com/paulrsm/dg/dg17.htm "As a result, work on a faster (shrunk) 68000 has been set aside and all hands are concentrating their efforts on the 68010. We understand that the 68010 will be the chip targeted for speed improvement. The good news is that the 68010 is pin compatible...
Interestingly http://bitsavers.trailing-edge.com/components/chipsAndTech/82C452_Super_VGA_Graphics_Controller_199109.pdf :
"The maximum display bandwidth is 200 MBits/s - 25 MB/s at 8 bits/pixel"
I wonder if this required faster DRAM chips for example.