Teacher, you have answered well. Did the scribes just pull a fast one on Jesus? Was Jesus getting smarter of were the religious leaders finally coming to believe in Jesus? While the forgoing sounds unlikely, the scribes for once took their hats off for Jesus. Not only did Jesus answer a question well, he also escaped the trap the Sadducees had set for him. The Sadducees had wanted to have Jesus shoot himself in the mouth  by having him contradict Moses. They knew that anyone who dared to contradict Moses was not a real rabbi and could very likely face the wrath of the people. Jesus seems to have known their intentions and took the opportunity to teach them a thing or two about the resurrected life.
Marriage is a human institution like no other. It is an institution that ensures that there is continuity in the human race, that is, that the human race doesn’t become extinct (and this was the point of the six remarriages in the hypothetical scenario presented by the Sadducees). Even Moses himself understood that much. Marriage as a human institution is thus concerned with the ‘earthly’ (the Sadducees also acknowledged this much in the scenario they presented, for if it were not so, then the first husband would not have been concerned about not siring children since they would have the opportunity to do so in their resurrected lives). In his response, Jesus reminds them of this fact: marriage is concerned with the ‘earthly.’ Men and women who are focused on the resurrected life would not be so much obsessed with the ‘earthly.’ They would not be obsessed with that which is not eternal. 
By saying that marriage belongs to this ‘world/age,’ Jesus was not belittling this important human institution. He was simply making use of what he was presented with. Marriage, as are all other human institutions and endeavors, do not endure. He/she who is bound for the resurrected life should be focused on that which endures: angelic life.