Quickly?: He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus.?

Translation issue, I think. Christ is speaking about His returning to the earth and referring to that end-time generation. The generation in which these events take place (the sign of His coming, etc.) will not p until all is completed. "This generation" isn't referring to the ppl He was speaking to at that exact moment.