Has the used market for these cars reached the point where the majority of them now have updated tensioners?

 

Turn over among owners is not a guarantee that the previous owners resolved the issue. Many are still running around out their because the owners didn't know or they were very lucky.
There is only one way to know for sure the condition of the tensioner : remove the cam cover.
Also keep in mind a lot of 1st gen have only been change to a slightly better 2nd gen and not to the final 3rd gen tensioner