I'm not sure that's true.  Say it becomes yet another fork, separate
(necessarily, at first, because it's a different image format) from
all of the other forks.  As long as most packages can be loaded into
it, it'll get used.  Maybe not by the people doing the forking (by
Scratch, say, or Squeakland), but by the majority of us who have a few
pet packages (in my case, Seaside, OmniBrowser, DabbleDB, etc) that we
can load into nearly any Squeak image and feel at home.  I'm pretty
happy to load those into a MinimalMorphic image this month, a Pharo
image next month, and a Cog image the month after, if there's some
compelling reason to do so - and 10x performance would certainly be
compelling.

A shared microkernel would be nice, but I don't think it's essential
in the short term to drive adoption of a new technology.