The Jetson TX1 Developer Kit is approaching EOL. Final orders from distributors will made by January 15, 2019, and NVIDIA will continue shipping Jetson TX1 Developer Kits through March, at which point those orders will be fulfilled.
JetPack 3.3 is the final JetPack to support Jetson TX1 Developer Kit. L4T sustaining releases for Jetson TX1 will continue to be made as deemed necessary. (L4T 28.2 was the most recent release.)
Note that NVIDIA Jetson TX1 module will remain available through January 2021. It is interoperable with the carrier board included with the Jetson TX2 Developer Kit as well as with various 3rd-party Jetson Ecosystem carrier boards.