Paul says that as a skilled, master builder he laid a foundation. Paul is clear about that foundation. The foundation is Jesus Christ. (1 Corinthians 3:10-15). He pictures others building on that foundation. “Building” must refer to Christian preaching and teaching. The building that will bring a bright future must be in keeping with the message as revealed by Paul and the apostles. It must be on the solid foundation.
In Ephesians 2, the image is similar. The temple of God, which is the people of God, is built upon the foundation of the apostles and prophets with Christ Jesus as the cornerstone. In the ancient world, the cornerstone was what gave the building orientation and stability. It was far more than just being decorative. The mention of the apostles and prophets provides us with another emphasis on reliance upon the inspired message about Jesus.
A solid foundation always produces a bright future. Now I realize church history (as well as the history of congregations) has times of challenge and discouragement. But those built on the solid foundation have the hope of being a part of an unshakeable kingdom. (Hebrews 12:25-29) Nothing stops those who are faithful unto death. Nothing takes away their reward. They have a bright future, because those built on the foundation are becoming a temple in which God will dwell.
Someday those on the solid foundation will hear the loud voice from the throne say, “Behold, the Tabernacle (the Dwelling Place) of God is with people. He will tabernacle (dwell) with them, and they will be his people, and God himself will be with them as their God” (see Revelation 21:3, my translation of the quote). The solid foundation leads to this bright future!