There has been no decision on how long to supply updates for 6.x
I intend to supply updates for a long time after the release of SME 7.0.
The end date depends on various things:
There being a continued demand for the updates
Fedora Legacy supporting 7.3
Strategic decisions from the development team
Support from the community for testing the updates
As the support for testing the updates is already quite low I expect this to be the eventual reason for stopping producing updates.
So to re-iterate, it is the intention of the maintenance team to continue supporting 6.x.