anyone can sell a2/a2 milk today but the brand name cannot be "a2 milk" - they have to come up with another name. They may use the term a2 milk on the label but not enough to confuse the public into thinking it is the brand "A2 milk" - hence it gets very difficult from a marketing point of view. That said, it will happen.
Before that however you have to have the milk supply.
The key patent which stops someone putting together an a2/a2 herd quickly is the one that A2M have on testing a cow to determine if it is a2/a2 by taking a sample of its tail hair. This is an A2M developed test and the patent doesn't expire until 2023. This is pretty important.
With regard to the USA - there are large numbers of a2/a2 cows according to Keith Woodforde. Some farmers have been converting their herds in anticipation of the growth of the a2 milk market. No doubt many of these are supplying A2M now. The question is who are the others planning to sell their milk too. I suspect A2M are the most likely purchaser of much of this milk given a likely move to production of A2 Platinum formula using US milk.
For others who want to convert their herds quickly they have a problem if they can't access the a2 patented test. For years there has been another method for testing whether a cow is a2/a2 but it is a far more invasive blood test. The A2M test is simple and non-invasive so can be done quickly. Even if you use the alternative method once you i.d enough a2/a2 cows you then need to aggregate them into viable herds, in the right physical locations. Thereafter to make any meaningful impact on the market you need a very large supply of milk which requires a very large $$ commitment to marketing to ensure you can move it quickly.
So for any significant competitor to appear they need to be convinced the market demand is there, then create the herds to a significant level, then once the volume of milk is available they need to put significant branding and marketing $$ behind it. If they start small they will have no impact on A2M given the size of the US market (the current small scale a2 milk producers in the US fall into this category). If they go big it will slow A2M's growth rate but not stop it, as it will will also be an endorsement of the benefits of a2 milk and imply the wider milk market is moving towards more a2 milk and associated products and less a1.
All of this takes time but it will happen. In the meantime A2M are establishing themselves as the pioneers and they own the all important name "The A2 Milk Company" and some protections on the use of the brand "A2 Milk" (although I am unsure on the strength of the these as A2M don't give much away on the detail of their IP) plus they have first mover advantage. First mover is only useful if you execute well. They are executing well. The arrival of any serious competition will suggest the demand for A2 milk has grown to such an extent that other companies can't afford not to be in the market. By his time A2M will have established themselves as the premium brand - particularly in the IF space.
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