My question; Is Topaz deprecating their Photoshop plugins or are my impressions and experiences a symptom of choices they have made in web design?
Yes, I think from everything Topaz have said, that the old plugins are part of their history. They explained when they introduced Studio that the current Plugin model was both commercially and technically unviable, and they needed a different approach, which was Studio.
Studio itself, with basic editing features, is free, but with paid for Pro features that didn't/don't initially match the capability of the stand alone plugins.
However, when the updates to a Studio Pro feature matches the original plugin features, you automatically get the equivalent Pro feature activated in Studio (assuming its a Plugin you already own). So far five Studio plugin equivalents have been activated for free in Studio (including Detail and Clarity).
You can run Studio as a Plugin from Photoshop, much as you did with the original plugins, except running them through Studio is much quicker, and the new design of Studio is allowing Topaz to provide upgrades to the Studio versions of the plugins that they couldn't have provided with the stand alone version.
The old plugins still work, and can be run from PS as before, or from inside Studio, and of course, you can now run Studio as a standalone program, including doing raw conversions, but its not something I have tried. Nor do I intend paying directly for any of the "Pro" Studio features, as I am just waiting for them to be automatically activated for free as they match the capability of "my already paid for" older stand alone plugins.
It looks as if there will be no long term updates to the old plugins, and the only updates will be through the Studio route. The reason the plugins are still for sale, I assume, is because Studio doesn't yet provide all the capability of the equivalent plugins.
Crucially, you need to open a new Topaz "Studio" account, with the same email address as your existing Topaz account, to get the automatic free upgrades to the Studio versions of the Plugins as they become available.
I confess, I found it all a bit confusing at first, and I had problems with the auto updates, because of how long ago I had bought my Plugins, but Topaz were very helpful and sorted everything out.
Cheers,
Graham