Two-dimensional semiconducting materials of the transition-metal-dichalcogenide family, such as MoS2 and WSe2, have been intensively investigated in the past few years, and are considered as viable candidates for next-generation electronic devices. In this paper, for the first time, we study scaling trends and evaluate the performances of polarity-controllable devices realized with undoped mono- and bi-layer 2D materials. Using ballistic self-consistent quantum simulations, it is shown that, with the suitable channel material, such polarity-controllable technology can scale down to 5 nm gate lengths, while showing performances comparable to the ones of unipolar, physically-doped 2D electronic devices.