Over the past couple of years, TJ has also shown a tendency to evolve the lineup quite a bit as the season has worn on.This is the best lineup as of today and should be getting the majority of minutes in January. As you said though it is a long season injuries happen, specific matchups, and/or there may come a time where TJ decides a role shake up may be needed and the top 8 will change. I fully expect we see Biliew and Watson keep working in practice and get on the the floor in meaningful minutes in Feb/March to help this year's team.
Last season Watson played fewer than 10 minutes in each of the "big" P6 non-conference games, played 4 minutes against Western Michigan, then 7 and 3 against Baylor and OU to start conference play. Then he had 7 straight games playing at least 10 minutes, then 5 straight playing fewer than 10 minutes (plus a few additional DNPs), and finally 4 straight to end the season where he played more than 10 minutes. Some of that variation was due to injuries, but some was also due to simply identifying different combinations of players that were working over the course of the year.
Even though there's a pretty clear top 8 right now (assuming a healthy Ward), I do think that Otz and company change things up enough that both Watson and Biliew will get meaningful, important minutes at some point during Big 12 play.