Indeed, virtually all new servers, desktop, and laptop computers being sold today have 64-bit hardware and operating systems. Some high-end cell phones and tablets also have 64-bit hardware and operating systems. However, the hardware and operating system are only part of the Y2038 issue. There are many other technical areas where Y2038 issues may exist, including application software, peripheral hardware, device drivers, file systems, databases, communication protocols, web content, and embedded systems. Computers with 64-bit hardware and operating systems are capable of running 32-bit software which may not be Y2038-compliant. Even 64-bit software may not be Y2038-compliant.
It is also important to consider that most of the billions of embedded systems today and likely trillions that will exist by 2038 will still be using 32-bit (or less) CPUs due to factors such as power usage and the higher cost and complexity of 64-bit CPUs. Many embedded systems will not experience Y2038 issues, but a significant portion of them may.