You may be correct on this, however, how many of the current SW users are using a paid-in-full version of SW2018? I suspect that the majority of 2018 users are people working at medium to large size companies.
My feeling is that a very significant percentage of current SW users are still on cracked versions of SW2013 or older. (and many of those still using a 5+ year old cracked version of MasterCAM as well).
A good number of the smaller shops I deal with have been using/testing Fusion 360 in parallel with their current CAM system, and quite a few of them say they will be dropping their maintenance contracts on their current software.
I jumped onto Fusion a few years ago during a special they ran which was $5/mo for 2 years. Now I will be on the $310/yr plan for as long as I remain on "auto-renew" (with 5-axis, probing, etc.). If Autodesk goes back on their word, well... I can always go somewhere else at that point if need be. For now (and probably the foreseeable future though), it's an awful lot of "bang for the buck", IMO.
PM