You can definitely play MGS5/V before playing 4, if you've played 3 you'll have 60% of the context needed. Peace Walker and Ground Zeroes make up the last 39%. IIRC the only context you'll get from playing 4 is a few things involving the Les Enfants Terribles project.

EDIT: Thinking on it, if anything playing MGS4 after V might actually enhance your enjoyment of the series as it was fully meant to be a bookend to the series.