The ATLAS experiment at CERN is planning a second phase of upgrades to prepare for the High Luminosity LHC, due to start in 2026. In order to deliver an order of magnitude more data than previous runs, 14 TeV protons will collide with an instantaneous luminosity of $7.5 \times 10^{34}$ cm$^{-2}$s$^{-1}$, resulting in much higher pileup and data rates than the current ATLAS detector was designed to handle. While this extreme scenario is essential to realize the physics program, it is a huge challenge for the detector subsystems, trigger, data acquisition and computing. The detector upgrades themselves also present new requirements and opportunities for the trigger and data acquisition system. Initial upgrade designs for the trigger and data acquisition system are presented, including the real time low latency hardware trigger, hardware-based tracking, the high throughput data acquisition system and the commodity hardware and software-based data handling and event filtering. The motivation, overall architecture and expected performance are explained. Some details of the key components are given. Open issues and plans are discussed.