It might still be alive and working as the desktop environment nowadays are progressing kinda slow (in the concept of usage, not functions/softwares), but al least desktop isn't dead yet but it's now more a productive platform than everyday life needs.
Some old but still working basic compiler examples are RapidQ/XBLite/GFA-Basic, and FreeBasic is still grow slowly, if PureBasic has stop sales there will some solutions available
I've switch to Mobile and HTML5 for a while and I think these thing might hit some limitation eventally, but I can't predict what will happen even in a few months coz the it world is now changing very fast.
The world is changing fast but it still takes a long time to get there! I'm still using Windows XP on most of my computers with no complaints.
And those that are too old now to use it functionally (internet and stuff) are still running fine on versions of Linux. I don't like the current direction that Windows is headed and so am looking seriously at further moving into Linux, but currently I still update my kids with Windows OS computers.
All things change with time but it still takes a lot of time for things to change, to any degree that you can no longer use them, and that includes operation systems.
Pure Basic too will end some time but even when it does, it too will be usable for many years to come. I would dare say enough time to adapt if necessary. I do enjoy coding in PB and I would say I'm safe with this for some time yet.
"What you are is what you have been. What you’ll be is what you do now.” -Buddha