What do your calculations tell you will be the purchasing power of a dollar when 1btc=$25mil USD ?
Discussion
The $25 million valuation I base on today's global wealth as measured in dollars.
There's not really a good way to guess a future true value based on fiat valuation of BTC without knowing how much the global monetary supply increases over that time frame.
I think we could try projecting it, based on recent money policy.
Once the transition happens, the BTC:USD price doesn't matter. All that really matters to anyone is purchasing power. If a Bitcoin buys you a house, great; if it buys you a cart of groceries, not great.