[Oni]

If you're referring to the traditional definition of social engineering (human exploitation), that has always existed and will continue to. If you're referring strictly to refunds/warranties, then it's a little bit different. Compared to 8 years ago, there's a huge difference in preventative measures. Companies that used to offer unconditional lifetime warranties have tightened what they offer. Shipments are checked closer.

It's fair to say that companies will improve these protections and social engineers will have to adapt to that. Like any form of security, it will always be a cat and mouse game. Like you said, some methods might get patched (like "did not arrive"). While more corporate firms like Amazon might adapt sooner, smaller or more obscure ones might never.

Put simply, human manipulation has been around for centuries, and will continue to serve SE'ers Indefinitely.

This entirely. Refunds/warranties might become less common, but that's not all social engineering is limited to.