In an interview with CVG, Sony Worldwide Studios President was asked what the PS4’s lifespan would be compared to the PS3. Yoshida then responded “I would say the same or similar because the PS4 has an incredible amount of RAM and I don’t think any launch titles need that 8GB of RAM. So there’s room for growth in both game content and system features”.
This statement suggests that the PS4 will be supported for at least ten full years.