Generally speaking, loading a ZEXP from an older version of Plone is equivalent to starting Plone 5 using a Data.fs that came from Plone 4 -- there's a decent chance the data will load, but any upgrade steps that are meant to transform the data for the new Plone version will not have run. In particular, with a migration from Plone 4 to Plone 5 you would end up with content that is still Archetypes-based rather than having been migrated to plone.app.contenttypes.