The Xperia 5 V has now been seen on Geekbench shortly before its official release. While the smartphone has been benchmarked with 8 GB of RAM, there are rumours that Sony is also planning to offer a 16 GB of RAM edition for some markets.https://www.notebookcheck.net/Sony-Xperia-5-V-shows-strong-performance-in-Geekbench-leaks-with-alleged-16-GB-RAM-model-also-touted.744731.0.html
The last time Sony put 16GB RAM on their smartphone was the Japan-only Xperia 1 iv Gaming Edition. I won't be surprised if 16GB RAM option is also limited to Japanese market only.