firm down
A combination "firm up" and "nail down"; often used to express a soft commitment to something or a lack of clarity around something that will eventually be fully committed to or fully clarified.
I'm like 60/40 to attend the Trials in Eugene, but I'll let you know when I'm firmed down.
Soon we'll need to firm down a date for when the new release is going to go out.
Soon we'll need to firm down a date for when the new release is going to go out.