As long as the South African are using the R4 as their primary rifle there is a chance that we will see more battlepacked .223 from them. There are plenty of other places it could come from though-Spain, Singapore, Malaysia, Taiwan, South Korea, Guatemala.......lots of places that use 5.56 and have for a long time. There is still Korean .30-06 on the market and they haven't fielded Garands in 25 years! It's a matter of time before something breaks loose. Many of the smaller nations don't even make their own ammo and though it comes from there it might actually be made by FN or IMI on contract etc.......
Since there is soon to be no more market in parts kits and ammo is so very high I believe the importers will find something. Even high capacity magazines have lost some of their luster as they can be domestically produced now and the parts ban will kill some of the demand anyway. They can only stay in business if they have something to sell. Other than ammo what else is there?