Xavier just started sampling to automotive clients and NVIDIA revealed the codename of Xavier's successor at its GPU Technology Conference. AnandTech writes the SoC is codenamed "Orin". It's a single-chip solution, but no in-depth details were revealed at GTC 2018.
Interestingly, NVIDIA claims a couple of Orins will be able to replace a Pegasus module. That would be a massive achievement:
Pegasus, as a reminder, is a pair of Xaviers each with an unnamed, post-Volta discrete GPU attached, with a total power consumption of 500W. So to replace that with a couple of single-chip SoCs would be a significant accomplishment – and presumably a massive bump in energy efficiency.