Supersessions are delt with using a combination of functionality. If the item is superceded in a BOM then the new item is entered in the BOM to replace the old using ECO or manually.
For sales order entry the Item is flagged as obosolet or Obsolete Use-Up(stocking types O or U) and a "Replacement Item" is referenced using the Xref program (P4104) there is a pre-setup cross ref type of "R" for replacement, however you can create your own in UDC 41/DT. That reference type code needs to be added to Processing option 3 in the "Cross Ref" tab against P4210.
If the original item is selected the user will get a warning that this item is obsolete and will then have to select the replacement using the row exit. A work round if you are on 8.9 or higher is to use the promotion functionality to automate the replacement.