Will God send us new light before Jesus returns?

I do not know of a statement from Mrs. White to the effect that no new light is to be revealed before Jesus returns. It seems to me that she always left open the possibility of our discovering new light. During her lifetime she did not dismiss anyone who came claiming to have new light, but rather she told them how to handle it: take it to the brethren of experience, lay it out before them, and let them determine whether they see any significance in it. If they do, fine—look for further opportunities to make it known. If they do not, let it alone. (See, for example, Testimonies, 5:293.) These instructions would have been unnecessary if there were no more light that could be revealed. Mrs. White wrote,

It is a fact that we have the truth, and we must hold with tenacity to the positions that cannot be shaken; but we must not look with suspicion upon any new light which God may send, and say, Really, we cannot see that we need any more light than the old truth which we have hitherto received, and in which we are settled. While we hold to this position, the testimony of the True Witness applies to our cases its rebuke, “And knowest not that thou art wretched, and miserable, and poor, and blind, and naked.” Those who feel rich and increased with goods and in need of nothing, are in a condition of blindness as to their true condition before God, and they know it not.—Review and Herald, August 7, 1894 (Counsels to Writers and Editors, 33).

While Mrs. White said we must always be open to new light, she also warned,

Satan hopes to involve the remnant people of God in the general ruin that is coming upon the earth. As the coming of Christ draws nigh, he will be more determined and decisive in his efforts to overthrow them. Men and women will arise professing to have some new light or some new revelation whose tendency is to unsettle faith in the old landmarks. Their doctrines will not bear the test of God’s word, yet souls will be deceived (Testimonies for the Church, 5:295).