Since the old model Trooper has essentially the same action as the Colt Python, Official Police, Officer's Model Match, and other mid-frame older Colt's, spare parts will be available for many years.
Gun Parts Corporation, Jack First Gun Parts, Brownell's, and Colt have parts, and will for some time, especially as Colt still makes the Python.
For repairs, Colt, Cylinder & Slide, and Pittsburgh Handgun Headquarters will continue to repair the older Colt's for many years.
The old Model Trooper can be seen as a "poor man's Python", since the Python is really just a Trooper with a different barrel, a better blue job, and a hand-tuned action.
As a side note: There are two versions of the old Trooper.38 Special guns. The early model had a firing pin mounted on the hammer, the later versions had the pin mounted in the frame, like the Python.