The stated goal of TSA is to create three checkpoint channels. 1) pre-check which will acommodate 85% of travelers, 2) current standard channel which will acommodate most of the rest, and 3) enhanced screening ("SSSS").
As people are shifted into #1, the # of lanes dedicated to pre-check will increase. But, it's not instant.
Remember, pre-check isn't a FF benefit of the carrier, it's simply that the initial program goals were met through FFP data.