Gregor's death can absolutely be read as a sacrificial act by Gregor himself. He has been slowly declining over several weeks, but when he hears his own beloved sister say that Gregor should just die and that he was a burden to the family, he lets himself die so as to relieve the family of the burden of caring for him and dealing with all the hardship he thinks he brought to them. The fact that the maid and not a family member disposes of the dead body plays into this attitude they all have toward Gregor by the end of the story.
We learn throughout the story that everything Gregor did in his life was in support of his family and that he worked harder and longer than even would have needed to if his father had been more forthright about the financial status of the family. But even upon realizing this, Gregor is forgiving and deferential to his father's decisions. Gregor sacrifices his youth and his happiness for the family. Once he is a bug he sacrifices his comfort and hides under the bed so as to not repulse his sister. He sacrifices his want of human contact by staying in his room. His death is clearly the final sacrifice he can make for his family and his death was imminent anyway.