Bitcoin is not and never dead for sure, its still much alive as price is moving upwards at a moment, if price falls back to $400 then we can say its dead.
Not even dead with $400 because it is a bigger amount compared to the amount at the start of this year, bitcoin has already increase substantially this year so I would not say it will die, the progress is continuing so we can see another increase in the coming months.
$400 price is not considered to bitcoin is dead already as you said its still a big amount and more than to the entry price of this year on bitcoin. For sure we would witness the price increase of bitcoin in upcoming months and years. Progress is normal for bitcoin because its becoming popular day by day and the adoption is possible.