I doubt they would feel sad about their technology being adopted by a mainstream language used by millions of developers vs. a research experimental language that many outside of research haven't even heard of before.
The number of programmers back then was much less than now, but even then I don't think Smalltalk was a top 10 language. I guess it depends on how you define mainstream, Smalltalk has/had its niches, some of which are still active. But there is nothing wrong with using research languages like self (which was never mainstream) to explore and develop new tech that can be applied to mainstream languages.
