No. Actually, Traveller: The New Era replaced Megatraveller entirely. It...didn't go well. So much so, in fact, that itnis a pretty direct analogy to 4E D&D.
I think you basically are right thouh: Traveller has a history that parallels D&D pretty closely, a Rollercoaster to an evergreen present.
We can go a step farther: while new variants do get released, Backgammon and Chess are fairly stable at this point. I thinkt he Crearice Commons release of D&D makes wild change to D&D-as-D&D sociological improbable.
Pretty simply a matter of material culture: injection molding was only invented around WWII, and then soon people figured out they could make dice easily in any shape. People.made dice in other shapes throughout history, but cubes are thr easiest to carve. Still the easiest to store and ship...