2. I have always understood that it won't be necessary to have plural marrage in the celestial kingdom because it is an earthly sacrifice. There will be no sacrificing in the Celestial Kingdom (or am I wrong there) Therefore there should be no plural marriage. (Please don't answer by tellling me there are more righteous men than women, that is putting such little faith in men that it makes me cringe. Heavenly Father, Jesus, and The Holy Ghost are all men and they are our prime examples. There has got to be a better reason than not having enough men, for me to accept that we are going to have plural marriage in heaven.
JOEL - #1. At arond 1831 Joseph Smith inquired of the Lord about plural marriage and learned that, when the Lord commanded it, a man could have more than one wife, the same as the ancient prophets of the Old Testament. The foremost reason why Plural marriage was practiced in the early days of the church is because God commanded it. Lorenzo Snow explained:
"He knew the voice of God—he knew the commandment of the Almighty to him was to go forward—to set the example, and establish Celestial plural marriage. He knew that he had not only his own prejudices and pre-possessions to combat and to overcome, but those of the whole Christian world…; but God…had given the commandment" [The Biography and Family Record of Lorenzo Snow, pp. 69-70 (Salt Lake City, 1884)].
We can try to come up with reasons why God commanded it, and I have explained some of those possible reasons in other questions on this page, but the bottom line is that it is not possible for us to completely understand why God tells us to do some things. Joseph Smith said to Brigham Young, "it is the work of God, and He has revealed this principle, and it is not my business to control or dictate it" (Brigham Young Discourse, Oct. 8, 1866, Church Archives).
The Book of Mormon makes clear that, the Lord will command men through his prophets to live the law of plural marriage at special times for his purposes (Jacob 2:28-30)
One possible purposes we do know is explained in Jacob when God says,
"For if I will, saith the Lord of Hosts, raise up seed unto me, I will command my people;"(Jacob 2:30)
The phrase, "raise up seed unto me" implys that when God feels it is important to accelerate the growth of His kingdom on earth He will command the practice. Besides this there are no other specific reasons given by God as to why He wanted them to practice plural marriage at the time He commanded it. To this day God has still never fully explained the actual reason for it. The Saints lived it because they believed God commanded them to do it. Most of the reasons we have heard of have come after the fact, from saints trying to explain it to church critics and to themselves. The reasons you give as well as others are possible explanations but are still the attempts of man trying to understand the mind and will of God.
2. Will plural marriage exist in the Celestial Kingdom? We already know it will exist there because all those women in the early days of the restored church who were sealed to one husband will still be sealed to him in the Celestial Kingdom. No new plural marriage covenants will be made once we get there, for that is an ordinance that must be performed while here on earth. However, the practice could perhaps be reinstated during the Millennium.
Even though it is an eternal doctrine, it is up to God to decide when we should live it. For those of us living right now plural marriage is not essential to our salvation or exaltation.