Google Chrome’s next update will move qualifying users to the 64-bit version automatically in the next update, 59. This applies to users who did not turn off auto updates.
Machines that have more than 4 GB RAM and are running 64-bit versions of windows are the ones affected. Since no one really turns off the auto update feature, pretty much everyone will be making the move.
32-bit applications have a limit of 4GB of RAM. Without tricks, 32-bit operating systems won’t see beyond 4GB RAM. Having access to more memory improves the performance of applications. Google claims this will also improve stability and security of the browser.
There is really no reason to stay on the 32-bit version, though. Gone are the days when 64-bit apps were not as stable. They now match and exceed the performance of their 32-bit variants. And entry-level computers these days come with more than 4 gigs memory.
Chrome is the current king of browsers. With a market share of 59%, they control a huge chunk of the internet.
Source: Chrome Releases.