Is a new Metal Gear game necessary?

Since the announcement of MGS Delta, I've seen people who want more Metal Gear games, MGS6 basically. The question is: Is it necessary? The mainline games, from prequels to the MSX games to the sequels, told us everything we needed to know, a story with beginning, middle and ending. They concluded the character arc of Solid Snake and Big Boss with MGS4. Is there more to say? Maybe MGR2 but what about the main "Solid" series?