The short answer is no, none of the Hass avocados being sold today are genetically modified organisms. They have virtually the same genetic makeup as they did nearly hundred years ago when Rudolph Hass grew the first tree from a seed that he purchased. The seed was likely cross pollinated when Hass purchased it, but the exact subspecies of the seed are unknown.
A genetically modified organism, or GMO, is one that has had its DNA modified through genetic engineering. This usually involves recombinant DNA technology, which transfers molecules from one set of genes to another. Genetic modification is done in an attempt to suppress or generate specific traits in the target organism.
Genetic engineering is not the same as natural cross-pollination, or breeding which has been done for centuries. The Hass avocado is a product of these processes which should not be confused with the modern development of genetic modification.
It is reasonable to assume that genetically modified avocados will eventually find their way to market. Previous attempts at modification were aimed at reducing the size of the pit and increasing resistance to certain fungi and pests, among other things. When genetic modification of avocados is successful at increasing yields and profits for growers, those cultivars will likely proliferate.
Genetically modified foods are, of course, a hotly contested topic with many people staunchly opposed to their use. I can see points on both sides of the argument, and don’t wish to get into that debate here. Whichever side you’re on, you can be sure that any Hass avocados that you find in your local grocery store have not been genetically modified.