'Real Housewives of Beverly Hills' -- Two Wives on the Chopping Block

The fates are pretty much sealed for two cast members on "Real Housewives of Beverly Hills" -- we're told producers are gunning to replace them next season ... because they're just not exciting enough.

Sources tell TMZ, there's a 95% chance Joyce Giraud and Carlton Gebbia won't be back for Season 5 -- they're just not involved enough in the series' story lines to justify their coveted spots in the cast.

We're told it became obvious Joyce and Carlton weren't jiving during the reunion show taping earlier this month -- all the other women had great chemistry ... and Joyce and Carlton were clearly outsiders.

But the feeling's not mutual -- at least for Carlton, who tells us, she'd love to return for Season 5 if she gets asked back.

Sources tell us, producers are already on the hunt for replacements ... you listening, Joanna?