Should Customers Wait for 5G Capable Equipment?
5G is not present in the maritime market right now, and probably won't be for a while longer than a few months. Peplink, as an example, does make one high-end device that has 4G modems with removeable modular modems that could be swapped out for 5G later. For customers concerned about high throughput in city streets I might advise you to wait, but for a boat 5G doesn't really matter all that much.
Technical Background:
There are two types of 5G networks being deployed, sub-6Ghz, and mmWave (also known as ultrawideband). mmWave (millimeter wave) runs around 30Ghz frequency, where normal cellular/LTE is around 2Ghz or less. mmWave is what AT&T and Verizon are advertising for super high speeds. Sub-6ghz (or 600-700Mhz in reality) is what T-Mobile is advertising, though they will start deploying mmWave also now that they merged with Sprint.
For Low Frequency 5G (ie: TMo), the speed benefit over 4G LTE is about 10% at the same frequencies.
For High Frequency 5G (ie: ATT, VZW), the speed benefit is enormous, but the range is about 1000 feet from the antenna.
5G On Boats:
So on a boat, you may or may not ever see a low frequency 5G network, but not having access to it won't matter for about 10 years when 4G gets shutdown.. 3G is just now going away. Unless you park your boat in the middle of Chicago on the river, you will likely never pick up a high frequency 5G network.. The range of that frequency is just nothing a boat will ever really benefit from and those networks are focused on high density small areas like downtown cores, stadiums, malls, airports, etc. You will see that carriers will literally mount an antenna on every street corner, building, light pole, etc in order to provide coverage, and even then the 5G signals won't penetrate a building's walls to the interior, requiring 5G repeaters/boosters (which aren't on the market yet) to project the signal into apartment buildings, etc.
All that to say, if you want 5G, it's not really possible right now and I wouldn't recommend waiting for 5G equipment in the case of a boat application due to the particulars of 5G networks.
Comparison with existing 4G LTE-A Equipment:
The Peplink HD1 Dome has a Cat18 LTE-A modem (Gigabit class) which will give you all the speed you can get from an LTE tower. The tower will be the limiting factor. The Peplink HD2 Dome uses two Cat6 LTE-A modems which are 300Mbps max each. You still won't ever hit these limits because about the fastest LTE I have ever seen was Sprint at about 100mbps for a single connection, some claim to get 150mbps but that is still well within the limits of Cat6 LTE-A hardware.