OU needs at least four more wins to get in the NIT IMO. Last year, the worst record for any NIT team was 16-14 by Georgetown, but they were ranked in the top 25 for most of the season (top 10 at one point, I think). They also played the #1 SOS in the nation. OU's schedule isn't that bad, but at 50 it's not going to do you any big favors, either.
A major conference team with 17+ wins has a shot at the NIT, but it's far from a guarantee. OU is probably on the outside looking in at this point. But based on what I've read here about how unresponsive this team is to Capel's coaching, it might not be a bad thing to just get the year over with and move on with whatever is necessary to get things fixed.