I wonder if such accuracy is necessary for emulating newer systems. I don't think my PS3 games are updating the graphics hardware mid-scanline. If modern systems have more relaxed timing requirements, then a much simpler binary translation may be enough. You no longer have to model the hardware, just the abstraction layer that the game itself is written against.
This is the premise of HLE, or high-level emulation. You emulate the CPU (if it doesn't match the current one), and then implement all the APIs it hits. It's more like WINE than BSNES.
The one place where you may end up emulating something with precise timing is the audio processor; the Gamecube and Wii for instance used a custom DSP that had to be emulated fairly precisely, after the instruction set was revere-engineered.
