Yes, technically speaking. That's one of the uses of "minimum firmware" drop-downs in "package submission" tabs. I remember reading (where?) that when you bump up the version there, the new package will be available only to boxes with that OS version onwards - and the older boxes will receive an older (the highest compatible) version instead. Akin to how things are in iOS, older devices download older compatible versions of the app. Note that said setting can only be
increased but can't return back to patch older version. The Co. staff can do more on their side but don't know what constitutes compelling reason.
In practice, don't know if approval of update of a "public" channel for 3.1 firmware can be negotiated now, since "legacy" got actively discontinued - TBD what a Roku* says? Worst case, your 3.1 version stays as it were for legacies and the new players (model# > 2222) get the more graphical scenes

PS. there ya go, Roku* spoked