God acknowledges that this land which He will bring them to is already the home of other people groups: Canaanites, Hittites, Amorites, Perizzites, Hivites and Jebusites are living in Canaan. Wondering if this was fair to those inhabitants? Of course, God, who created the earth, obviously has the right to distribute living space as He sees fit. However, God has been extremely fair and patient with these inhabitants of Canaan.
Over 400 years ago (from the time of those Israelites living in Egypt) God had already known what would happen in the future. He had told Abraham (who was at that point still called Abram):
Moses would probably have been glad to hear that the Lord was about to rescue his fellow Israelites from slavery in Egypt. Since he apparently knew about Abraham, Isaac and Jacob, he probably also knew about God's promise to bring the Israelites back to Canaan after about 400 years in Egypt. The time was right, and Moses probably rejoiced to think that their release from Egypt was at hand.
However, I think it was a bit of a shock for Moses to hear God's final message: