There are currently no plans to do official BOINC releases optimized for specific platforms. Since BOINC uses so little CPU time, the savings from this would be on the order of CPU seconds per actual days.
Since BOINC is open source, however, developers may compile their own version of the client optimized for a specific platform.
Projects which use the BOINC infrastructure may release their applications in optimized form. Care should be taken to ensure the optimized versions are sent only to the proper processors.