https://news.ycombinator.com/item?id=10906999
Apple is far from having a secure phone right now. NSA certainly has ways to bypass this based on my attack framework and their prior work. They just don't want them to be known. They pulled the same stuff in the past where FBI talked about how they couldn't beat iPhones but NSA had them in the leaks & was parallel constructing to FBI. So, the current crop are probably compromised but reserved for targets worth the risk.
That said, modifying CPU to enable memory + I/O safety, restricting baseband, an isolation flow for hardware, and some software changes could make a system where 0-days were rare enough to be worth much more. Oh yeah, they'll have to remove the debugging crap out of their chips and add TEMPEST shielding. Good luck getting either of those two done. ;)