The equation of exchange will let you calculate the value of any currency, if you have an estimate of its velocity. In Bitcoin's case, it's:
(price of 1 BTC) == [(World GDP in dollars)*(fraction of economic transactions using bitcoin)]/[(supply of bitcoins)*(bitcoin velocity)]
Your argument is so general that it uses figures from the world today to create an argument about the world in X years time?
Your thesis is based on annual global wealth being $1.3 trillion. As I've said, the world in X years time (when btc = $1million) is so far into the future that this figure is utterly ludicrous (unless the global economy fails to grow at all in those many decades...)
In my hypothetical scenario, 1.3 trillion was the total mining rewards in one year, not the global wealth. You are fixating on the random numbers I picked to illustrate my point, and you're missing the actual argument.
To put it another way: people will spend roughly the value of all mining rewards in an effort to get these rewards. The best amount of security for the Bitcoin network is only very crudely related to the value of these mining rewards. That is a problem.