Opera 12.x and earlier (Presto-based versions) were available in both i386 and amd64. Next was the unstable builds, and continued to be so for some time after the switch to Chromium.
The first public Chromium-based build for Linux was Opera Developer 24.0.1537.0, builds prior to that are Windows or Mac only. So there was over a year in which the Linux versions received no update. The first actual stable release for Linux was Opera 26.0.1656.0.
They may eventually release another i386 build (based on Chromium also), but I don't know when.