Sony may be on the verge of releasing a version of the Xperia 1 II with 12 GB of RAM, but it will not necessarily offer any performance improvements on the standard 8 GB model. To that end, Geekbench has shown the performance limits of going from 8 GB to 12 GB of RAM, with marginal improvements in single-core and multi-core tasks.
https://www.notebookcheck.net/The-Sony-Xperia-1-II-shows-the-performance-limits-of-having-12-GB-of-RAM-over-8-GB.499932.0.html