Yes, up to 512 bits since Skylake. But there are very few real-world tasks that can make use of such wide data paths. One example is media processing, where a 512-bit register could be used to pack 8 64-bit operands and act on all of them simultaneously, because there is usually a steady stream of data to be process using similar operations. In other tasks, where processing patters can’t make use of such batched approaches, the extra bits would essentially be wasted.