As the model gets smarter its security hardening will get smarter as well. Back in the day when search engines were a curiosity all you needed to do to get your page to the top of the results was to insert a bunch of keywords in white text in the background. This is pretty much the same kind of attack.
Would you say that Google search has found a way to beat SEO spam sites? If the comparison of the development of search engines and the development of AI chat holds up, then it seems to me that creating prompt injection will trump defeating it in the long run.