Moving up is always a concern but we do our upmost to maintain forward compatibility.
Certainly the inroads files like XIN, alg, dtm you are good moving up as essentially little has changed here.
From a dgn content standpoint, specifically with Openroads tools being introduced is where object level changes were required, this is why 397 mstn is required as the base platform to preserve these objects. Certainly previous SELECTseries geometry needs to be updated and this is managed on first opening the dgn in the later version.
If you have any specifics please contact us so someone can help.
Regards
Ian