JOEL - Only God knows the answer to this question. I can only say for sure that it is very possible that there could be new entries into the D&C, because the heavens are not closed to us as long as we have prophets living on the earth.

I do know that we have been told that the talks we hear in General Conference every six months are as good as scripture. So in a way new revelations are being given to us all the time.
God has told us:

"And this is the ensample unto them, that they shall speak as they are moved upon by the Holy Ghost. And whatsoever they shall speak when moved upon by the Holy Ghost shall be scripture, shall be the will of the Lord, shall be the mind of the Lord, shall be the word of the Lord, shall be the voice of the Lord, and the power of God unto salvation." (D&C 68:2-4)

And President Joseph Fielding Smith said:

"What is Scripture? When one of the brethren stands before a congregation of the people today and the inspiration of the Lord is upon him, he speaks that which the Lord would have him speak. It is just as much scripture as anything you will find in any of these records and yet we call these the standard works of the Church. We depend, of course, upon the guidance of the brethren, who are entitled to inspiration."(Joseph Fielding Smith, DOCTRINES OF SALVATION, vol.1, p.186 (1954). 4 ibid., p.243.)

So because of this principle, there may not really be any reason for a lot more to be added to the D&C, unless some very significant revelation should come to the prophet that would provide some special understanding about a point of doctrine or if there were some new thing that God wanted us to do.
The last thing that was added to the scriptures was "Official Declaration - 2" about the revelation on the priesthood in 1978.