"Why is my qualified disability trust not taking the 4050 exemption in the final year?"
That is probably designed into TurboTax Business as a result of the trust terminating and, hence, distributing all of its assets (with income, gains, etc., being carried through to the beneficiary(ies) in the process).
You can override this in Forms Mode by unchecking whatever box is checked on your 1041 and checking the QDist box, but there really is not much of a point to the larger exemption in the final year since you will get an IDD (income distribution deduction) which will, essentially, result in the exemption being wasted/unused.
By the way, the exemption is $4150.
