Is it true that Bitcoin is limited to 7 transactions a second which are recorded in 1 block every 10 minutes?
No. It is not true. 7 transactions per second is an estimate that was calculated by making some assumptions about transaction size. Those assumptions are unlikely to be true in most cases. In reality the average number of transactions that bitcoin can confirm per second with the current block size is likely to be significantly less (closer to 3 transactions per second).
Does that mean 1 block can only hold 7 x 60 x 10 = 4200 transactions?
That depends on the transactions. If the transactions are small enough, then the current block size can actually hold more than that. Realistically with the typical transactions, blocks can hold about half of that.
How can Bitcoin be scaled for a global audience?
People have been discussing this very topic for over 5 years. There have been hundreds of threads about it on bitcointalk. Several potential solutions have been proposed with various levels of support and technical merit. Perhaps take a little time to read through some posts on this forum before making assumptions and declarations
With the growth of Bitcoin usage this has to be a drastic limitation oversight by Satoshi?
Oversight? What makes you think that Satoshi didn't have any plans regarding this? What makes you think that his plans are still the best possible solution 8 years later? What makes you think that there is nobody else in the world after 8 years of study and use of the protocol that can come up with any better way to handle growth?
Clearly to compete with the likes of visa etc then block size needs to be increased to process more tps?
There are many people that don't have any desire for bitcoin to "compete with the likes of visa". There are others that feel that bitcoin could compete, but that many transactions can be handled "off the blockchain". Then there are others that feel that the protocol should be updated to handle more transactions per block (or more blocks per hour). I really can't believe that I've chosen to get involved in yet another of these pointless discussions just to re-state all the things that have been stated so many times before.
If so, what's the disadvantage to larger block size?
Greater consolidation of mining power. Increased orphan blocks. Increased cost in running full nodes. It is assumed by many that scarcity of available block space creates an incentive for users to include transaction fees which will eventually be needed to maintain hash power for transaction confirmation.
Slower confirmations?
Not sure why it would lead to slower confirmations. Care to explain?
I'm surprised satoshi wrote nothing on upscaling this.
I'm not sure why anything he wrote about this matters, but since it seems to be important to you, here you go:
It can be phased in, like:
if (blocknumber > 115000)
maxblocksize = largerlimit
It can start being in versions way ahead, so by the time it reaches that block number and goes into effect, the older versions that don't have it are already obsolete.
When we're near the cutoff block number, I can put an alert to old versions to make sure they know they have to upgrade.
He might have however I'm not aware of his writings.
Well, if you are not aware of his writings, then why do you make assumptions about what he has (or hasn't) said?
Here's an idea. Try reading the white paper. Then try reading Satoshi's writings. Then try searching for discussions about the things that you want to know about. Then after you've done all that, see if your opinions about the technical details of bitcoin have changed.
White paper:
https://bitcoin.org/bitcoin.pdfSatoshi's writings here at bitcoin talk:
https://bitcointalksearch.org/user/satoshi-3