The first iPhone to come with support for the 5G network will most likely appear in 2 years.
What is unknown is which company will be the manufacturer of the 5G modem. Apple has an agreement with Intel, but the company is not satisfied with the performance of the chip. The biggest problem is the overheating of the 8060 chip.
The good news for Apple is that Intel is working on the next generation of modem 8061. The bad news is that there is no guarantee that the chip will be ready for the first 5G iPhone.
Apple might also consider a deal with Qualcomm, but the two companies are in a bad relationship due to recent lawsuits. Qualcomm also has a problem with the modem that has heating issues with some of the manufacturers which are testing it.
Heating is also a load on the battery because the energy from the battery is not being properly used.
The reason for heating is the spectrum on which the antennas radiate. Heating is such a problem that it is felt on the outside of the phone.
Apple is also in talks with MediaTek but it looks like it is a very distant plan B.