The speculation is that there will be no mechanical Dura Ace (but not confirmed). No one has said anything about 12 speed Ultegra, let alone whether there will be a mechanical option. Ultegra mechanical is one of Shimano’s biggest OEM sellers and eliminating it may not be a wise move financially.
Shimano has never released updated DA and Ultegra in the same year…doing so just undercuts sales on DA as most people would opt for the less expensive Ultegra. If you only have a DA option for the first year, early adopters have no choice but to pony up for DA.
The wild card in all this is COVID and the massive delays it has wrought on the industry. Whether that forces Shimano’s hand to release both groups in the same year remains to be seen. But I have not seen / heard any rumors of 12 spd Ultegra being imminent.