Surely there would be some sort of stat that shows the change in ladder position from certain points in the season(pre, during & post origin as an eg). That would be interesting to see the hit and miss nature of some teams from those that start the season well, to those that fall away etc. Regardless it's likely to be a mad scramble for the eight from rds 20-26.
No doubt you could compile such a stat.
It is pretty easy to look at past season's ladders and get a snapshot of how teams went from round 7 to 26.
For example, last year after round 7 the top 8 was:
1) Broncos- slipped a bit just before and around Origin
2) Cowboys- ditto
3) Sharks- kept winning until the last few rounds, then entered the finals on a losing streak
4) Eels- stripped of points
5) Storm- rose steadily each week to be minor premiers
6) Bulldogs- just slipped right at the end of the season and bundled out of final
7) Raiders- rose steadily all season from here
8) Rabbitohs- dropped more than won from here and finished 12th
Finalists Titans and Panthers were 9th and 10th, and the Eels were stripped of points.
After round 26:
1) Storm
2) Raiders
3) Sharks
4) Cowboys
5) Broncos
6) Panthers
7) Bulldogs
8) Titans
So basically last year, after round 7, the teams in the 8 continued to do well except the 8th placed Rabbitohs (who still only finished 2 wins out of the 8) and the Eels, who were stripped of points, and the two teams who came into the finals were 9th and 10th in round 7.
In 2015, the top 8 after round 7 remained the same in round 26 except the Knights, who fell away from 7th to last, and the Sharks who virtually swapped fate with the Knights, going from 15th to 7th.
That doesn't fill teams 11 to 16 currently with a lot of optimism I suppose, but in 2014 four teams dropped from the 8 from round 7 to 14 (Tigers from 2nd to 13th, Titans from 4th to 14th, Dragons from 6th to 11th and Eels from 8th to 10th) and teams 9 (Storm), 10 (Rabbitohs), 11 (Roosters) and 13 (Cowboys) rose to the top 8.
(In 2013 there were two changes, Broncos and Titans dropped out, Sharks and Bulldogs climbed in, in 2012 there were two changes, Dragons and Roosters dropped out, Raiders and Rabbitohs climbed in).
You can scroll the records easily, but in general, most the teams in the top 8 after 7 rounds remain in the top 8 after 26 rounds, but there are a few changes, usually about 2, and usually it is usually teams from 5th to 8th that drop (to 9th to 12th) and teams from 9th to 12th that climb to 5th to 8th.