The objective of the EuCARD2 WP10 (Future Magnets) research activity is to demonstrate high-temperature superconducting magnet technology for accelerator applications by building a short demonstrator dipole with an aperture of 40 mm, operating field of 5 T, and understood field quality. One of the magnet requirements is of small inductance, for use in long magnet strings; hence, the superconducting cable must have large current-carrying capacity, in the range of 10 kA at the operating conditions of 4.2 K and 5 T. An initial down-selection of the cable material and geometry resulted in the choice of REBCO tapes assembled in a Roebel cable as the baseline layout. In this paper, we described the requirements derived from magnet design, the selection process that led to the choice of material and geometry, the reference design of the cable, and its options. Activities have started to address fundamental issues, such as tape performance and tape processing through the cable construction, and key performance parameters such as cable critical current under stress or magnetization. Here, we report the main highlights from this work.