One of the standard responses to Summorum Pontificum is that there is already adequate provision for the celebration of Mass according to the Missal of Blessed Pope John XXIII.
Summorum Pontificum allows priests to celebrate the Mass privately and for people to attend. It also allows parish priests etc. to arrange public celebrations at the request of a stable group of the faithful without further permission. If provision is already adequate, there should be no significant growth in the use of the old rite as a result of the freedom allowed by the Motu Proprio.
I suppose there is no sense arguing about this right now - we will all see in time who was right.