I've re-implemented their secure monitor as open source software twice. It has no bugs. I've re-implemented their kernel as open source software. It has no exploitable bugs. Software hax isn't happening unless NVidia made bootrom mistake (unlikely imo).
xbox one has successfully gone an entire generation without software compromise vulnerabilities. Nintendo's secure monitor has 300 functions. Its kernel has ~800. These are tiny binaries, small enough that it's possible to get them right. I'm less confident in NVidia's code, but.
Software hax really seems unlikely to me, I would plan as though it will never happen.