Furrtek has just posted a progress update to his Neo Geo FPGA project. It looks like there’s good progress and the sound chip is next. Furrtek’s Patreon subscribers can read the full post here: https://www.patreon.com/posts/progress-october-22015121
It’s my personal opinion that open-source FPGA cores are essential to preserving the original experience without original hardware. A big thank you to Furrtek for open-sourcing this work!: https://github.com/neogeodev/NeoGeoFPGA-sim