Applying the existing CC 2.0 licenses to data, as extensively documented, has significant problems for OpenStreetMap, among them:
1. "leaky" in jurisdictions where factual data may not be unambiguously copyrightable;
2. inconsistent, inequitable or unpredictable scope of share-alike terms;
3. unclear attribution requirements.
3 was partly addressed in CC 2.5 but 1 and 2 remain as issues. If CC is prepared to address them in CC 4.0, that's very welcome; at present ODBL is the only share-alike license to consider these issues, via its contract/database right approach (1) and its Produced Work terms (2). ODBL is an excellent license but is of course not the only possible answer.
CC's approach thus far has of course been to mandate public domain for all data. This is clearly preferable for the scientific community, where attribution is volunteered at any rate. However the geospatial data market is predominantly commercial, and many therefore feel the case for requiring share-alike and attribution through terms is stronger.
The "public domain only" approach is also inconsistent with CC's attitude elsewhere, which encourages you to licence on your terms. If CC is stepping away from this, that would be a welcome development.