Board Thread:General Discussion/@comment-166.137.88.23-20130610185107/@comment-180.200.190.132-20130616035044

Solidus doesn't have the Middle-Eastern history, and the room Eli is in has Middle-Eastern vibes to it. The jacket, the jackal teeth, the hair, the "youth who curses his fate", he looks like he could be 12 (Liquid's name), plus Eli being the Biblical brother of David (Solid Snake's real name), all point to Liquid more than they point to Solidus.

So it's probable that it's Liquid, very unlikely to be Solidus, but still could be a new character.