Right now you need 4 SO-DIMMs: 32 GB each. you can get that already in Lenovo's P72. That is a 17" workstation laptop though, so it has more room available than others, but it's not totally crazy, especially if a vendor used a different format instead of bothering with DIMMs. I don't think Apple's gonna do that anytime soon though, it's too niche for what they do.
Hynix has a 32Gb LPDDR4 chip on their catalog, listed as "in production". If a laptop was LPDDR4 compatible, you could fit 128GB in two double-sided SODIMMs.
Do you know how much physical space that would take? I highly doubt you’ll see it any time soon.