I would sell all my bitcoins if I had 1,000,000 and the price went to a few million dollars a coin.
I would sell all my Bitcoins if the bitcoin price goes up to $1 Million or drops down to $0.001/coin.
I would sell all my Bitcoins if I could get some millions of USD by doing so
If the price went to a million dollars per BTC, though I might reconsider selling them :p
i would sell all my bitcoins if they go up to 1 million dollars each, then i would be rich 
Hyperinflation aside, the only way Bitcoin will ever reach $1 million USD would be if it reached a market cap and status equal to all modern national fiat currencies combined. Alternatively, the economy might be large enough in the future to accomodate a $1 million BTC price and still have it coexist with a much weaker fiat.
But by then, it's fair to assume that Bitcoin would be accepted everywhere that fiat is also accepted. So why would you want to shift your net worth from BTC to USD at all?
Bitcoin wouldn't be seen as being the inferior, less desirable currency anymore. In fact, it might just be the exact opposite. By selling your coins when they're $1 million each, you would be moving away from a currency that has grown consistently stronger over the years to one that can be printed at whim and has been slowly dying while losing its value. In fact, by dumping your coins when they are worth $1 million each, you could actually be selling your coins at the worst possible moment.
I mean why should I? I will think of multiplying my bitcoins rather then selling it.. Just imagine Bitcoins after 10 years.. It's gonna be huge and i would be really rich and wealthy if i possess some good number of bitcoins.I would be the richest. 
. But i hope so it will. The problem is many people can't take a risk for waiting the price of bitcoin get higher. They sell it when it increase a bit. Well, maybe rich people can wait. But people like me who don't have many bitcoins will hard to take a risk like That.