following can be risks
1. master data objects should not get deactiavted
2. Transactional data objects should not get deactivated.
3. data loads should not fail
4. data should not disappear..
as far as i see there should not be any issue new nav fields will get added but they should not harm existing fields unless SAP has reduced some of the objects length but that will never happen.
You can also check with SAP to get their inputs.
Thanks and regards
Kiran
