There is still plenty of room for improvements with specialized design and software even if physics is limiting the improvements in general purpose cpus.
New interconnect technology like on chip photonics, specialized hardware like artificial neurons, and new software designs to take advantage of new capabilities provide plenty of room for future growth.
Even if hardware stays still there is plenty of improvement to be made in algorithms, coding and working with ever larger networks.
I'm betting on A.I. and autonomous cars.