Once D&D
Officially they've never used edition numbers.They have insisted that it is "just D&D". I don't think they are going to change the name or increment an edition version.
(And I wish they would. By precedent this seems like a 3.0-3.5 change if the playtest is indicative of the final product.)
Check the back cover of the 5E PHB.Officially they've never used edition numbers.