I don't think there's any real timeline to get rid of Oracle just that new projects won't be using it as a DB and eventually it will no longer be in use.
Like eventually nobody will be using mainframes... except they are still there, and somebody is still cashing cheques for their support.
Ironically, it's Oracle itself who is busy self-destroying. The move to cloud-based subscription services, where switching to competitors can be so much easier, looks good in the immediate but it's pulverizing their stranglehold on partner ecosystems, and making their long-term outlook more fragile.
