The short answer is Absolutely. We believe that work (baptism, marriage, etc.) is done in our temples for those who have passed away and have not had the opportunity to do those things to enable them to achieve exaltation. That is one of the main purposes of our temples (there are over 140 of them around the world) is to do the different ordinances for those who are deceased.

The Lord will never prevent someone from having the oppertunity to recieve exlatation. Those who died in this life without a spouse or sealed to there spouse in a temple can still have there work done to enable them to receive exaltation.  
 
For those who died too young this work will be done during the millenial regin of Christ when the righteous dead rise again. The reson why this work will have to wait till then is be cannot know if or whom they have courted and joined with as an eternal partner in the Spirit World.