If the absolute increase in 'making' the playoff is 5 % and every conference has an 'equal chance' except for the Big 12 which is falling behind then the chances are:

SEC:81.25%
ACC:81.25%
Pac:81.25%
Big:81.25%
Big12:75%

Which would increase to each conference being 80% probability after B12 adds a championship.

So, the B12's chance of *not* making the playoff decreases from 25% to 20%. In real terms they go from missing once every 4 years to once every 5 years.