http://www.bloomberg.com/news/articles/2016-02-24/apple-fbi-...
Apple has indicated that they're going to continue to keep increasing the security of their products in the future, which may make it impossible to update firmware to the Secure Enclave (or at least require the user's permission first), but that's actually a weak measure.
I'm not sure why tech people think that technical means to accomplish zero knowledge is the holy grail, that will never trump having the law on your side. Congress could pass legislation (like CALEA for tech companies) that would require everyone to design their products to make them accessible to law enforcement any time they want.