If you feel like you want to get ready for running on another platform, or using Docker as it matures, then I'd suggest the first step would be to move your databases to a neutral third party provider. With that in place, you can still run your code on the dotCloud PaaS, or anywhere else. As Docker and the ecosystem around it mature, there will be many more options.
I work for Docker Inc on the dotCloud PaaS and manage the support. If you have more private questions, you can reach us at support@dotcloud.com
/Andy