This from what I can make of it is NOT an upgrade or update from the current version. The current version is 6.07 and has not been updated in months. As far as I can tell no changes have been made for High Sierra but it does run under High Sierra. However given the instability of the product that I have incurred since V6 was released, combined with the abysmal tech support that I have been given (4 documented issues and questions that have not received closure since April when they were asked/reported)
My personal recommendation would be to avoid this product at all costs unless you absolutely have to have it.
However in all fairness in the short time I have been using it in High Sierra, it does seem more stable in High Sierra than in Sierra.
However High Sierra has also introduced some new issues in Dragon Dictate; particularly in Apple Mail as caching and correction no longer seems to work. I have not reported this to Nuance as their seems to be no point to wasting my time to do so, given their seemly reluctance to fix anything - i.e. the Dragon Safari extension has been crashing randomly since V6 came out many months ago and that has been reported.
I would not be suprised if Nuance comes out soon with a new expensive paid upgrade which turns out to be primary bug fixes for this version, along with the usual marketing spiel about how it is now High Sierra compatible and runs faster, as they usually do with likely another price increase. I feel they are able to get away with all of this, as they know they have no competition on the Mac Platform and seem to do their very best to take full advantage of that fact.
As previously pointed out if you decide (in my opinion) to be glutton for punishment by purchasing this product I would second the previous recommendation regarding not getting their headset, but finding a good one, preferably wireless to use with it. FYI: Bluetooth headsets are not recognized by Dictate.unless it has a USB dongle or USB connection in its stand.
I use a Plantronics Savi 740 wireless that give superb results and connects to my computer, my landline (or VOIP) and my mobile phone and has a range of over 300 feet that allows me to roam while speaking or dictating. It allows connections between the various inputs and the long lasting rechargeable batteries are changeable on the fly. It also does a fairly good job receiving dictation with the headpiece sitting in its stand. While a bit pricey it I feel it is worth every penny for what it does.
Dictate is also supposed to work with Mac built-in microphones, so if you have such a system, you might want to try that first before investing in a headset.