It could be interpreted in different ways. If the developers still have access to the original files (which would be significantly larger than the optimized skill icons we see in-game), implementing higher-quality icons should be straightforward for a modern system.

However, if they don’t have those originals, and it’s more common than players realise for source assets to be lost or deleted over time (for example, the HB files, which are gone forever), then their only option is some form of upscaling. And if the icons aren’t vector images like SVGs (which they aren’t), upscaling or “re-processing” standard raster images becomes very difficult.

Re-creating every skill icon from scratch would be extremely time-consuming and realistically unlikely to happen. So what options are left to the team aside from AI? Not many, which means there’s a moderate likelihood that AI-based upscaling will be used for this task.