They were working on a new version AN-124 with CF6-80C2 engines, but I don't know if that's on on-going program. Awfully quiet if it is still happening.
I never heard of a planned retrofit, although if it did happen for new production it would make the engineering for a retrofit quite a bit easier.
I know for fact that is was considered for the Volga-Dnepr fleet but I guess it turned out to be too expensive / complex. Yet, they, just as Antonov or the Russian Air Force have to find a way to make those
Progress D-18T last (and there is already some serious canibalism going on...). Don't know what will be the eventual outcome but something has to give...