[Belle Noir]

I don't see larger yorkies going extinct.
Though the breed standard calls for under 7 lbs, and for the history of the breed, it's been bred to be smaller, the fact that there are still many larger yorkies being born promises that they will continue to be born.
Every yorkie bred to the standard, every show champion, has somewhere up close in it's pedigree, a dog that went over max weight. For example, if a female is an excellent dog in all respects, except for size, (say she's 8-9 lbs) I can see someone breeding her, because they know the size can be corrected, especially if she comes from a line of dogs that run standard size. This keeps the larger genes into mix.
Not only that, a dog can carry genes for larger size, even though they are standard size themselves. There are a few teapots on this site that come from standard sized parents. If a dog is 5 lbs, and comes from a litter that produced a 15 lber, there is a high chance that 5 lb dog, if bred, could produce a larger yorkie.

And I will also add that again, there is a demand for larger yorkies. Especially if you're talking about a family with children that want a hypoallergenic dog. Most people who breed to the standard will not sell to a family with a child under 10. I can understand that, because a 6 lb dog IS more fragile than a 15 lb dog.
But let's be honest and real, when you're talking brand loyalty, you hook them when they are young. Breed loyalty is the same thing, so people that have positive memories with a certain breed when a child are more likely to gravitate to that breed as an adult. Do we not want people who are looking for a hypoallergenic breed to look at the yorkie, which we know carries less dander in their coats, due to the silky nature of the coat.. or do we want them getting labradoodles that 1) may not be hypoallergenic, 2) more than likely is nothing more than two random dogs thrown together, one a poodle and one a lab (maybe), 3) more than likely has parents with zero health testing done on them, and 4) could well have behavioral issues from being poorly breed, and even more poorly socialized? Larger yorkies are practically tailor made for families with children.

The issue then becomes the ramifications of people breeding for the pet market, because if you're breeding larger yorkies, that is indeed what you're doing. And we KNOW there is a demand for these dogs.
I do not have a problem with someone making the choice to breed for the pet market. But should someone decide to breed over standard size yorkies, like those who wish to breed non standard colors, yet remain reputable in the eyes of the greater yorkie community, they should adhere to a strict standard of health.
Basically, if color breeders have become more or less accepted/tolerated, at least those doing everything right except for breeding outside of standard color, then there should be no reason that size breeders could not also become accepted/tolerated, if they're also doing everything right, except breeding outside of standard size.

The issue becomes the "doing everything right" part, since we know that most people breeding for the pet market short cut on the important things like health testing of the parents.