Stick with 6x6 or try 645?
I got a 'cord Vb last year to upgrade from a Seagull. It's a great camera and quite discreet when out on the street, but the fixed lens is limiting. I am sure, however, that its no better in any respect than your 124G. It also needed the film transport and shutter repaired which cost nearly as much as the camera. Having used the square format regularly now for a year or so, I bought a Bronica SQ to allow me to use various lenses. It is far more precise in its operation than the Rollei, and much more versatile with interchangeable lenses. I agree with other advice; keep using and enjoying your 124G until it breaks, or no longer suits your photography.