Adam Thornton noticed earlier today that devtoolset-6 is no longer available from some of the mirrors we use to install packages, and according to
it's almost a year past its formal retirement date. Moreover, devtoolset-7 is only a month away from its formal retirement date, so I propose we go straight to supporting -8 only rather than both -7 and -8 (though I have no objection to continuing support for -7 for a bit longer, especially if it helps the transition - I just wanted to RFC dropping well before it too becomes urgent).
While we should obviously test this before implementing it, there have been enough reports of the stack building successfully on newer compilers that I don't anticipate problems, and I don't think that needs to block RFC adoption.
I'm giving this a short time window in case the CCB wants to take quick action before the weekly goes out this Friday; I'm not familiar with the details, but my understanding is that the lack of availability of devtoolset-6 may cause problems with that.