Yeah this looks like a
direct sequel to Peace Walker.
I'm under the impression that it is Chico at the very beginning. Funny how there was speculation about Chico being a young Liquid when Peace Walker trailers came out
The voiceover briefing by Kaz Miller says as much that Chico and Paz are being held in there. The burnt-face villain (srsly wuts up with that) says something about 'her' not suffering for long as per the kid's request, and by the end of Peace Walker it was obvious that Chico had a crush on Paz - so it would be in character for Chico to try and man up for Paz's sake. The kid in the demo looks pretty spot-on compared to the pre-rendered art in PW, too.
And, of course, Chico works for Big Boss.
So at the moment most of the implied evidence points to Chico being that fucked-up kid (seriously a headphone jack jammed into his chest ew), and Paz being dead. Admittedly it's wierd how Big Boss would look way older if that was the case, but I think it's fairly strong implications.
Of course, that'd raise some questions about what happened to Amanda =/
I like how the first level is somewhat reminiscent of the first level in the original,
.
"Kept you waiting, huh?" is a staple introduction line in the MGS series.
also, "Age hasn't slowed you down one bit" was one of the first lines of dialogue in the first MGS (Colonel Campbell to Solid Snake).