Pilatus/old redeye;
The upgrade is in the estimates, but that doesnt mean it'll be sanctioned. Its purely a cabin refurb, not an overhaul. Although not the newest avionics, the aircraft is doing plenty of flying in the training role. With the imminent arrival of PC9 students to the BE20, its no harm letting them learn what a basic T instrument layout is, and how to fly an IF approach on needles rather that the new screens, moving maps and HUD's they'll have learned on since they joined. Theres already a partly integrated GNS(you can couple it to the AP) and a standalone GPS installed.
In terms of a replacement, your logic is compelling, but Capital Expenditure is a big no-no, whereas current expenditure is ok within reason. Its all about budgets; easier to spend $3m on a refurb than $1m on replacement. And dont blame the Air Corps; they're the rules used across all govt departments.
regards,
Freespeed