DETROIT — General Motors is expanding its high-end GMC Yukon lineup to include a new "AT4 Ultimate" model as part of updates to the large SUV for the 2025 model year.The new model will slate in between the luxury "Denali" and "Denali Ultimate" models. The automaker declined to discuss pricing for the new AT4 Ultimate, but the Denali models currently start at roughly $77,300 and just under $100,000, respectively. The current AT4 model starts at $73,500.Denali models, now in their 25th year, have become a cas ...