They're slowly phasing it out. They've killed both iOS and Android Cortana apps, and I'm guessing it'll be gone from the next iteration of windows. Suffice to say, it's clearly not a part of their future road map, and not the driving reason why they're investing in ChatGPT. They've made it clear that their purpose here is to enhance Bing and challenge Google's dominance of the search market. Cortana has nothing to do with it.