The X55 is also fast, promising maximum download speeds of 7 Gbps and transfers of 3 Gbps under ideal conditions.
Above all, this should lead to smoother devices. The 7 nanometer manufacturing should contribute to the X55's energy efficiency from the start, but it also uses tricks such as 100 MHz envelope tracking and adaptive antenna tuning to minimize the Electricity consumption when you are on a 5G network. You should not need a big handset or a bulky addition to enjoy a higher speed than LTE.
The device manufacturers already have samples of the X55 and the modem should join the shipping equipment by the end of 2019. Essentially, Qualcomm tells you when the 5G will become really practical. The X55 is expected to usher in a second wave of 5G phones that should not make excessive compromises in the name of speed.