Doubling the transistors on a regular chip might achieve double the performance doubling the qubits on a quantum computer can provide an exponential speedup depending upon the kind of problem it is trying to solve. Dwave has shown speed ups of 10,000 time or more by doubling the qubits in their quantum annealing systems.
IBM Q scientists have successfully built and measured a 50 qubit processor prototype. Expanding on the 20 qubit architecture, it will be the next-gen IBM Q system. IBM aims to demonstrate capabilities beyond today's classical systems with systems of this size.
The first IBM Q systems available online to clients will have a 20 qubit processor. This new device's advanced design, connectivity and packaging delivers industry-leading coherence times (the amount of time to perform quantum computations), which are double that of IBM's 5 and 16 qubit processors available to the public on the IBM Q experience.