AMD hasn't officially announced its Navi 14 GPU, but after showing up in a Linux driver in June and the CompuBench database in July, the rumored Polaris successor will probably arrive sooner than later. Linux users should be ready when it does--Phoronix reported that Navi 14 support is set to be back-ported to the Mesa 3D Graphics Library with the Mesa 19.2 release that's expected to make its official debut within a few weeks.
Navi 14 is believed to be a smaller version of the Navi 10 GPU found in the Radeon RX 5700 that debuted in July. We don't yet know what products based on the Navi 14 will be called, but the RX 5500 or RX 5600 are likely candidates, based on the CompuBench database results from July. These will likely be lower-end graphics cards that offer a performance bump over the RX 500 series but don't match the performance of the RX 5700 lineup.
Developers worked to bring Navi 14 support to Linux regardless of the current dearth of information about the GPU. That support was originally expected to debut with the Mesa 19.3 release, because Mesa 19.2 was recently deemed feature complete, but Phoronix spotted a request from AMD RadeonSI Gallium3D driver developer Marek Olšák to back-port Navi 14 support to Mesa 19.2 that was made on August 26. (More information can be found here.)
Mesa's release calendar has release candidates for Mesa 19.2 debuting on August 27, September 3 and September 10. Release candidates for Mesa 19.3 aren't expected to start rolling out until October, with the final release candidate scheduled for a November 5 debut. That means back-porting Navi 14 support to the 19.2 release instead of the 19.3 release could prepare Linux users for the upcoming GPU two months sooner than anticipated.