I actually have thought about this too, but not in terms of $1,000,000 A share price, which is probably closer to 20 years away than 10. Think about the implied rate of return on BRK's non-cash and non short term fixed income investments if you think you can get to $1MM in close to 10 years; it would have to be nucking futs. Then again, I hope you are right!
What I have thought about is that each year more A shares convert to B shares, the A shares grow more relatively powerful since they have 6+ times the voting power.
The conversion can only go one way so over time. More and more long term holders will die or diversify, Warren's donated shares will likely be converted to facilitate sale as the B's become more relatively liquid and the A's become an even more exclusive club. Institutional shareholders will gravitate incrementally towards the B's.
Over time the ratio of voting interest relative to economic interest of the A shares will start to get interesting, particularly after Buffett dies.
At the end of 2011 there were 938,244 A shares and 1,650,806 total A share equivalents. The A shares commanded a 56.84% economic interest and 89.77% of the voting power. By my calculations, conversions caused A shares share of economic interest to decline by 2.3% in 2012, but their voting power only declined by 0.91%.
Hypothetically, if 1/2 of the A shares converted tomorrow, the A shares would have a 27% economic interest, but still command 71% of voting power, if I am doing my calculation correctly ( 447K A shares +1.8B B shares /10000 = 626K total votes of which the A shares would have 447K)
At its most extreme, the A shares could convert to a point where a 13% economic interest commands 50.1% of the voting power.
All this is moot and probably not worth thinking about since Berkshire is a controlled company and will remain so, but I just think it will be interesting to watch over the years.
I wouldn't be surprised to see a meaningful premium develop in the A shares over time, since a liquidity discount can be arbitraged away and more long term oriented holders may see it prudent to preserve their voting power