ODBL and CC-BY-SA are different enough that it would probably be difficult to declare compatibility in either direction. ODBL isn't much used yet, so the easiest way to maintain interoperability in the world is for people to continue to not use and/or ODC to retire it. :) That said, CC is happy to have any discussion predicated on maximizing the value of the commons. Certainly that's how we intend to approach development of version 4.0 of the CC license suite.
I'd recommend any non-software copyleft project participate in CC-BY-SA 4.0 discussions and keep an upgrade path to that license open. It may well be that OSM contributor terms could provide that path, as could a highly custom negotiation as provided by FDL 1.3 (which provided a brief window for massively collaborative projects like Wikipedia to migrate to CC-BY-SA), but utilizing those paths are much more costly and time consuming than a version upgrade of the same license.