there's a misconception here; we always release all modules at the same time and the intention is that you should always use the same version for each module: mixing different module versions is not expected to work at all.
Why would you use the older FileCacheStore with the newer core ?
Consider that Infinispan just loads and stores the blobs of what the user adds to the cache, so it's up to you to make sure that data serialized / marshalled with one version of your application can be restored by newer versions of your application.
The Lucene Directory is an exception as the directory module defines the externalizers as well; in cases such as this we don't change the serialized format in minor versions, unless the feature is experimental. To upgrade a Lucene index stored in version 4.x (where it was marked experimental) you can simply make a copy of it to a filesystem, then copy it in the new grid.