Then have both.
Unlike 16 bit to 32 bit it most simply is a recompile about 90% of the time unless you have assembly or something specific. My guess is the ugly Netscape API for the plugins which Chrome used to support until last year and of course Firefox is built upon this.
Newer atoms anyway are 64 bit. In the old days this would have been obsoleted in 3 years. I would have laughed at you in 2004 if you told me most things are still 32 bit 10 years from now. XP is still freaking alive too in a few places. I am just surprised what happened?
But the web unlike MS Word 2003 can't keep staying old and these things are slowed down by supporting obsolete platforms both hardware and software. Smooth scroll still does not work right in chrome because XP is so ancient and they still have to support it.