So what are the current SPLAT User Base numbers?

That is confidential company information. No business would share that.

Well, it is. Its owned by Gibson and not gone Chapter 11 or insolvent or anything. They're just ceasing development. 
 
Hah, 'just'. But you know what I mean.

you can easily find the steam user numbers https://www.google.co.uk/search?ei=xGoVWtKuH4qma-3fo5gE&q=sonar+steamdb+users&oq=sonar+steamdb+users&gs_l=psy-ab.3...4692.4984.0.5155.2.2.0.0.0.0.85.150.2.2.0....0...1.1.64.psy-ab..0.0.0....0.NioTv2FuhJk
but i've no idea how this compares to direct sales

20 years ago, customers actually had a serialized "Account ID" and mine was just over 200,000, so the "millions" may be an accurate number of "total registered users" in the past 30 years... many of whom (most likely) received a product with a piece of hardware or only bought a product one time. Bear in mind that number is not indicative of "revenue stream" in any way...
 
The Steam numbers are interesting... Since 4/2016, "SteamSpy" shows roughly 8000 "owners," which does not mean active (i.e., up to date). The "191.5 median hours play time" sort of indicates a one-time purchase, and that most only used it for a few months. Even with a 20:1 ratio of software purchases to Steam usage, that is under 200K (since 2016)... How many are "active" (i.e., paying forward) is most likely significantly less (and "life time" owners can no longer be considered revenue stream).
 
Unfortunately, life time updates will attract those most likely to cough up money, and only serves to remove them from the revenue stream... without hardcore new sales (even lifetime ones) behind that, the lifetime users become dead weight from a financial perspective.
 
If "millions" of active (paying) members were accurate (which it isn't)... Gibson could have kept lifetime updates rolling and paid off a nice chunk of their debt...