As of 8.3, the latest storage stream version is still 7 (the same since Pega 7.1.8)
There is no functional impact to changing storage stream versions. You can change the version at any time (and even change it back if desired). The storageversion prconfig setting controls how blobs are written to the database. Your existing blobs in the database will still be version 6 and still be read by the system.