"Is Lean software development currently a million miles behind what is truly possible?"
I have asked myself this question because it turns out that many Western manufacturers that are believed to be lean - and indeed are accredited as such - turn out to be nowhere near when the experts weigh in. A particular example is given in the book of a North American manufacturer that had been awarded the Shingo Prize for its lean-ness and was latterly visited by Toyota's Supplier Support Centre. They slashed 93% of the supposedly lean production time. 93%! They were just miles of the mark.
So, I wonder if - despite believing we're on top of software development practices - we are going to be surprised by a completely left-field player wading in and showing us all up with defect free software written in 5% of the time for 10% of the cost at some point in the near future.
My bet is yes, we are, only perhaps not in such a dramatic manner. The reason I'm sure that we're no-where near the mark for true lean-ness is that the core cultural values required to successfully follow the example of TPS are just as poorly embodied in our software industry as they are our manufacturing industry. However, software development being such an "immature profession" does give it a slight advantage in trying to move towards a lean culture, in that there are fewer entrenched ideals and practices that would need to be changed.