This is a slightly lesser priority than the other non-forward-secret cipher we're removing in T147199 , but we'd still like to remove this as soon as reasonably possible so that we can reach 100% forward-secrecy and remove most of the motivation for anyone attacking our private keys.
Current informal analysis indicates that the overwhelming majority of the 0.25% (and declining) of our requests which use this cipher are not from outdated user agents, but rather due to outdated and/or mis-configured outbound corporate TLS proxies which actively downgrade the connection security of modern clients behind them. Assuming this analysis holds up, we can probably try to run a CN campaign targeting these users in hopes of reducing that percentage further before we eliminate the cipher (whereas in the 3DES case, the bulk of the affected UAs are too old for CN to work at all).
The first step here is we need to run better analysis on the UAs choosing this cipher, try to confirm percentage which are due to corporate TLS proxies vs truly outdated UAs, identify any major outdated UAs that might warrant modifying this plan.
Assuming the bulk are in fact bad corporate TLS proxies and there aren't significant oudated UAs to worry about, we'll probably set a date a few months out for final cutoff and begin running a CN campaign to warn affected users and encourage them to talk to their IT department about fixing the issue.