I don't think you will find a new MG progression coming out any time soon. I asked Mark a similar question last week (in lieu of the new GXII release). His reply was - if it ain't broken, don't fix it, and I tend to agree. The success we have had here in NZ with the MG66 in club, and more so national events last year, was brilliant. Why change a winning formula.
You may see some slight cosmetic changes perhaps as time goes on, but the internals look set to stay as they are while the motor is as competitive as it is.