For it to reach that number, probably needs to be more, though not impossible.

The entire gold market is worth roughly $8 trillion currently, which is mostly a store of value market. At $1 million, bitcoin would be worth $21 trillion (when all coins are fully mined), quite a bit higher than the gold store of value market.

Though, perhaps money from other stores of value, like real estate and collectibles would also venture in...

I wouldn't say it's impossible that bitcoin achieve that valuation while mostly "only" being a store of value, but I agree that it may be difficult.