Well that just sounds like most US jobs (i.e. at-will employment).
And if the point is that you're clarifying with your employer that you're looking for an exit (even if it's not immediate) it probably means the employer (and maybe you are helping) is interviewing for your replacement with the goal of eventually finding it. Hence my curiosity that it's been 2 years and they haven't got a new CTO.
As a company with a strong focus on smooth 3D rendering I imagine it’s quite difficult to find a CTO who can top John Carmack, and if he’s willing to stick around then why rush it.
And if the point is that you're clarifying with your employer that you're looking for an exit (even if it's not immediate) it probably means the employer (and maybe you are helping) is interviewing for your replacement with the goal of eventually finding it. Hence my curiosity that it's been 2 years and they haven't got a new CTO.