This is already available and being piloted by several networks. @susevans might have concrete numbers. There was an announcements of the upgradability module here that the Interchain team provided: Channel Upgradability and Fee Middleware: A Closer Look at Relayer Costs and Incentivisation | by IBC Protocol | The Interchain Foundation | Medium
As for relayer-side support for ICS-29, it’s ready. I detailed some of the status of efforts from the Hermes team here. Upgradeability support is not fully ready yet.
I would not consider ICS-29 as the end-state for relayer needs, however.
Very much in favor of creating a working group to tackle this issue holistically, centered on the $Atom’s interests.