Do we have examples of such plugins that are currently hindered by MusicBee's 32-bit preference?
i think the OP means some (and even most last years) VST plugins.
BUT!
on one hand: support for 64-bit VST plugins theoretically can be added to 32-bit MB version.
on the other hand: MB anyway will be compiled as 64-bit app sooner or later.
on the third hand (

): there are many 32-bit native plugins for MB, which source code is unavailable.
P.S. i believe that the best solution would be to have both 32-bit and 64-bit versions of MB during some time. MB is written in VB.NET; .NET allows recompilation to desired architecture by simply choosing an item from a dropdown list. but MB also has win32 external dll dependencies, and i'm not sure if it's so easy to switch their versions too.