I do hope you are overly pessimistic,
We got several good years out of KDE's Plasma 4.
So after they get the kinks out of KDE's Plasma 5 I would hope for
several years of undisturbed use before they marshal the resources
to start on KDE's Plasma 6 with the new MistForm interface. In the
interval I may well die of old age or one of my allergies.
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http://www.sussex.ac.uk/newsandevents/pressrelease/id/40212>
bliss - ever somewhat hopeful.