FOCUS (Fast Monte CarlO approach to Coherence of Undulator Sources) is a new GPU-based code to compute the transverse coherence of X-ray radiation from undulator sources. It combines analytic descriptions of the emitted electric fields with massively parallel computation on GPUs, thereby reducing computation times by up to five orders of magnitude with respect to standard codes. Here we report on recent developments of FOCUS, including new functionalities and some performance optimizations. We also show results for current third-generation facilities and more modern, low-emittance X-ray sources close to the diffraction limit. Finally, we discuss future upgrades and highlight possible perspectives.