Stinger, the MGS game that announced a few months ago was a "prequel" to MGS V called MGS: Ground Zeroes. THIS is the actual MGS V (or Ground Zeroes is being renamed).
And the text thing is pretty damning because the "Phantom Pain" logo is used with Metal Gear Solid font and when you use the same font to write METAL GEAR SOLID V, it matches up perfectly with the lines.
But don't let that evidence win you over:
1. The guy in flames, its Colonel Volgin from MGS 3. Want more proof? Wearing the same pants.
2. Soldiers in the trailer are wearing FOX Unit outfits.
3. At the beginning, it shows some petals floating in the air...same as the ones shown during the Boss fight in MGS 3.
4. The bandage wrapped around the protagonists head that covers his eye? Same eye that Big Boss has a patch over.
5. IDENTICAL scar under right eye that Big Boss has in Ground Zeroes. IDENTICAL.
6. The creator of Phantom Pain is a man named Joakim....anagram KOJIMA.
7. At the VGAs, people who worked for Konami were wearing "Phantom Pain" or "Moby Dick Studios" shirts.
8. Flaming whale? Unicorn? Forget that imagery....PSYCHO MANTIS is shown at the end.
If you're wondering, "What? When was Big Boss ever in a coma?" Well, this fits in with MGS lore. Big Boss was in a coma at one point and this is when Zero extracted his DNA to create the Les Enfantes Teribles (sp?) Project. AKA the project that created the Sons of Big Boss, his clones: Solid, Liquid, and Liquidus Snake.
tl;dr, it is a MGS game.