The Lexar Professional 633x SD card, announced at CES earlier today, is the largest capacity SD card available to date at a whopping 1 TB. Despite its large size, the card is somewhat disappointing in performance; the 633x is rated at 95 MB/s write and 70 MB/s read. It also supports VSC Class 30, which means it should hit at least 30 MB/s when recording video. This should be adequate for 4K footage, but higher bitrates and higher resolutions may suffer.
https://www.notebookcheck.net/Lexar-announces-first-commercially-available-1-TB-SD-card.393646.0.html