“I predict that, no later than 11:59 PM Mountain Time, 31 December, 2050, the festival known as the Calgary Stampede will have ceased to exist.”

My reasoning is threefold:
DECOLONIALISM:
The current popular sociopolitical trend on this continent, which in my opinion has matched or even exceeded environmentalism in popularity, is that of decolonialism. Essentially, it is based in a presentist revisionism of North American history, coloured by a cultural Marxist view of past events, symbolism, and policy-making. I believe the virulence and increasing power of this new ideology is going to put a great deal of pressure on, among many other things, this festival to transform itself into something more in line with "twenty-first century" sensibilities (meaning, cultural Marxist demands).
ANIMAL RIGHTS:
There has been for some years now pressure from animal rights activists to end livestock-based sports at the Calgary Stampede, promulgated via advertising and interviews in the media establishment. If the number of people subscribing to this view in Calgary (or willing to travel to Calgary when the Stampede is underway) reaches a critical mass to the point where they stage protests outside the Stampede grounds, create internal disruptions or even dangerous provocations within the Stampede grounds, this annual event will go from being a celebration of Plains rural culture to being a source of sour sentiments.
DEMOGRAPHIC CHANGE:
Calgary, like other cities in the geocultural region formerly known as the Great American Desert, was founded on a Euro-Indigenous culture. However, mass immigration to Canada from the Indo-Pacific has been steadily changing (its proponents refer to it as "enriching") the face of the Canadian population. The federal support for a diverse mosaic model of Canadian society, rather than an integration and assimilitory model, has allowed the creation of parallel societies within the country, whose members seek to live more or less as they did in the country from which they or their parents emigrated. Combined with a decline in the number of Canadians who farm, ranch, or otherwise live in rural areas (all rodeos are intrinsically linked to the rural North American way of life), the Calgary Stampede is going to become increasingly an event that Calgary residents will feel ashamed or awkward about attending - seeing it as a quaint relic of a bygone era.
Given the above reasons, I believe that by the abovementioned deadline, the Calgary Stampede will have been prohibitted, disbanded, or changed into a new festival unrelated to its current form.