In today's economy , there are around 5 trillion dollars , if you consider all economies.
Even more
Okay , take it as 6.3 trillion , assuming there are all 21m BTC mined.
That will still be 300k , which is much lesser than necessary to cause a problem resulting in need to further divide Bitcoin.
It is unlikely that Bitcoin will ever cross a million $ , but I expect it to definitely hit the 10k range.
People who expect it to reach 1m in a few years are extreme fanatics.
Comparing Bitcoins future growth to the 300x boost it saw ages ago is stupid.
If Satoshi told 2 people about BTC when he first envisioned it and tripled the Bitcoin enthusiasts in a minute , we should not expect that to happen again in a minute.
TLDR; Bitcoin will rise , but even if it becomes as big as USD is now , it will be under 40k$ per Bitcoin (of todays USD value)
We will not need to further divide BTC in a long long time and if we do , we will have far more capable devs waiting to do so.The world is not aware of BTC, it's still in its ignorance..especially peoples with ridicolous government currencies (so excluding USD, EUR, GBP, JPY, etc. that should be the less interested)