If a RST of information saved using SAV command has not been done when migrating from one AS/400 to another (IFS has not as yet been used as such by users). What implications might this have for future use of the IFS? IBM's books are a little thin on what is actually saved/restored this way.
The SAV is generally used to save all of the IFS (Now called HFS??) information on your system. This would include the installed directories and HFS systems including any custom HFS systems you may have created. I would think that unless you are installing executable objects, or modifying parameters for the Web server(s), the impact should be minimal. If you are using your system as a file server, or for e-mail or other nominal IFS/HFS services, it could impact the configuration of those services.
On the other front, using the RST command, objects can be restored based on a number of parameters just like the RSTOBJ command. The linking, ownership and authorities could be impacted. There are no documents that really detail this, but it can be derived from the output of the RST command detailed in appendix 184.108.40.206 of the OS/400 Backup and Recovery V4R5 (SC41-5304-04) located in the AS/400 library.
Based on what I know and can derive from the documents that I have found, the ownership of objects, authorities, ASP (If your system is partitioned into multiple ASP's) can be changed by the system or overwritten. Additionally, link definitions can be impacted (however unlikely this may be). The easiest way to determine the overall impact this operation can have is an old trick of looking at all of the possible error messages. They usually indicate how bad it could get.