Apple's online store in the U.S. is currently showing delivery estimates of up to 4-5 months for many Mac mini and Mac Studio configurations with upgraded amounts of RAM. The delays are occurring amid a severe global memory chip shortage driven by surging demand from companies building AI servers that require large amounts of RAM. For example, a Mac mini with an M4 Pro chip and 64GB of RAM ordered from Apple's online store in the U.S. today is estimated to ship in 16-18 weeks.
Not gonna happen with Apple’s SOC. But you can upgrade the SSD. I bumped mine to 2TB relatively painlessly with a aliexpress module.