The debt will be written off at some point, when HMRC tells Steve Gibson he either has to collect it or write it off.
But I agree, it's a different world now. There's no way Boro can hope to compete with Chelsea, Man City, Man Utd, Liverpool, Everton, Spurs, Arsenal, Newcastle, Leicester, Villa, West Ham and a few others. So the target now is promotion and hope to win the mini league of about 8 "just hope to stay in the league" teams.
Right now, if I was Steve Gibson, I'd be more concerned about staying in the Championship. A leaky defence and goal shy attack are hall marks of relegation teams. The fact that there are few teams facing points deductions might save Boro but without that I'd say Boro are more likely going to be in the 3rd tier next season.