Could Christ have come before 1884?
Here are a couple of references that qualify.
The long night of gloom is trying; but the morning is deferred in mercy, because if the Master should come, so many would be found unready. God’s unwillingness to have His people perish has been the reason for so long delay (Testimonies for the Church, 2:194). 
The angels of God in their messages to men represent time as very short. Thus it has always been presented to me. It is true that time has continued longer than we expected in the early days of this message. Our Saviour did not appear as soon as we hoped. But has the word of the Lord failed? Never! It should be remembered that the promises and threatenings of God are alike conditional.
God had committed to His people a work to be accomplished on earth. The third angel’s message was to be given, the minds of believers were to be directed to the heavenly sanctuary, where Christ had entered to make atonement for His people. The Sabbath reform was to be carried forward. The breach in the law of God must be made up. The message must be proclaimed with a loud voice, that all the inhabitants of earth might receive the warning. The people of God must purify their souls through obedience to the truth, and be prepared to stand without fault before Him at His coming.
Had Adventists, after the great disappointment in 1844, held fast their faith, and followed on unitedly in the opening providence of God, receiving the message of the third angel and in the power of the Holy Spirit proclaiming it to the world, they would have seen the salvation of God, the Lord would have wrought mightily with their efforts, the work would have been completed, and Christ would have come ere this to receive His people to their reward (Selected Messages, 1:67, 68). 
For more information, read our document "Ellen G. White Statement on the Apparent Delay of the Second Advent".