This has already been settled in the EU - from a tax perspective, the sale is happening where the customer placing the order lives, which typically coincides with an address in the same country.
Now something like this is bound to come, from the new treaty, to all G7 countries, which hopefully means it will trickle down to the G20 at the least.
The main issue is not rules on sales though - it's cracking down on profit-shifting masqueraded as IP transfers and licensing. Hopefully that too is being cracked down on.
First, this is not a treaty, it is an annoucement. To make the announcement a "real thing", each country needs to go back to their own legislatures and pass laws, and in those countries that are federal, they need to somehow get their states to pass laws. That then needs to trickle down into account changes, jurisdictional changes, etc. None of that has happened. What has happened is that leaders got together in a conference and issued a joint press release of an intention to address a certain problem within a framework of certain types of solutions. Think of it like the Kyoto agreement -- there is a big difference between popping some champagne corks and actually getting stuff done.
Now something like this is bound to come, from the new treaty, to all G7 countries, which hopefully means it will trickle down to the G20 at the least.
The main issue is not rules on sales though - it's cracking down on profit-shifting masqueraded as IP transfers and licensing. Hopefully that too is being cracked down on.