This won't happen. The platform default is one of the most decisive factor for the market share and Apple has a full control here. Unless they do a critical mistake at IE6 level, Chrome won't likely have above 10% iOS market share.
That statement is much, much less true than it once was -- some quick searching puts Chrome at about 66% of desktop market share (despite neither of the two dominant desktop OSes shipping Chrome as a default), and the two default options (Chromium-based Edge and Safari) combining for about 25% of desktop market share.