The thing with native x64 O/S compatibility is NOT that audio will sound any smoother or better and all that nonsense.
The thing is that x64 hosts can adress much more RAM than x86 hosts, so people working with massive sample libraries that pre-load their samples into RAM (like myself) prefer accessing more than 3GB of RAM for increased responsiveness and performance regarding their sample playback.
If they, like myself, use a native x64 host software for doing that, then the plugins they use have to be x64 compatible. If they're not compatible, they won't work, can't be loaded, can't be used.
There ARE so called bit-bridges like jBridge etc. which act as "translators" to make x86 plugins available and work inside x64 host applications -and the other way round- but these bridges are pretty buggy, because they're not tailored to fit specific plugins but to stay pretty general and fit "most" plugins.
Also, these bit-bridges are containers, "plugins that load plugins", so when you open the GUI in your host to modify some plugin parameters, host-related commands like spacebar for play/stop etc. won't "go through" to the host. Completely cripples workflow for let's say mastering purposes and ruins the hectic play/pause rapid fire during mixing.
Doesn't sound like a drastic drawback, but if you're doing serious work on your DAW - it is.
Yes, "they work". But just because they work doesn't mean it's good that way.
Now the critical point is - user XYZ, who is a bedroom producer and uses maybe a drum sampler and some Kontakt strings, probably won't ever use 3GB of RAM in one of his projects and therefore doesn't need or depend on x64 compatible stuff; he can just stay with his x86 host in maybe his x64 O/S and happily continue to use x86 plugins.
But user ABC, who is a promising and known producer of (sampled) orchestral scores, will need and use all the RAM he can get his sweaty little hands on, so to him native x64 compatibility for the host and his plugins is essential.
Think he might want to spend his time re-starting his host a thousand times per day because the unreliable x86/x64 bit-bridge crashed it again, runining another 15 precious minutes of his work time, just because he has to put up with the sad fact that his essential everyday-use plugins are being held back from evolution and not ported into a current format?
I myself have switched to using x64 host and plugins only, because it meant an improvement to my DAW's overall performance and responsiveness when working with large sample libraries.
Which, of course, means I had to drop Waves and some other nice plugin gems that aren't x64 compatible, but there are enough alternatives from other developers to completely make up for this loss.
I can't be bothered with deliberately provoking host crashes or ruining my workflow, just to help developers avoid progress. For me, if a plugin is not x64 compatible it means it will empair me, so it's plain uninteresting = dead.
x64 architecture has been around for 8 years now in the Windows world, since XP x64 came out in 2003. More than enough time to adapt. If you (as a developer in general, not focused on outsim) haven't yet, or aren't at least still working on porting x86 stuff to x64, then I assume you don't wish to support my needs - so I won't support yours, meaning: one less sale.
I know I'm not the only one thinking like this.
EDIT to explain what this means:
Developers without native x64 versions of their plugins will slowly but surely be left behind, and their produrcts will remain to be used only in outdated setups. To any commercial developer, this would mean certain death, as competition by x64 developers will become too strong - if it isn't already.
So if SynthMaker stays x86 only and won't support exporting native x64 plugins, either VST or VSTi, a lot of small commercial developers will probably give up struggling with a working environment that only enables them to create outdated formats, and turn to an environment that will make their plugins up-to-date again.
I'm pretty sure a lot of potential future SM customers will be scared off by the fact that their possible future products might only be interesting for a tiny percentage of "old dogs" who don't support the x64 movement because they don't understand it or have no need for it.
Let alone the bad reputation SM plugins have with plugin devotees already. Long loading times, high CPU munch, and now it turns out they're also incompatible to 8 year old technology... Time to do something, I'd say.
-atheism is a non-prophet organization-