"AIRSPEED is a term that can be easily confused. The unqualified term airspeed can mean any of the following:
a. Indicated airspeed (IAS) - the airspeed shown by an airspeed indicator in an aircraft. Indicated airspeed is expressed in
knots and is abbreviated KIAS.
b. Calibrated airspeed (CAS) - indicated airspeed corrected for static source error due to location of pickup sensor on
aircraft. Calibrated airspeed is expressed in knots and is abbreviated KCAS. Normally it doesn't differ much from IAS.
c. True airspeed (TAS) - IAS corrected for instrument installation error, compressibility error, and errors due to variations
from standard air density. TAS is expressed in knots and is abbreviated KTAS. TAS is approximately equal to CAS at
sea level but increases relative to CAS as altitude increases. At 35,000 ft, 250 KIAS (or KCAS) is approximately 430
KTAS.
IAS (or CAS) is important in that aircraft dynamics (such as stall speed) responds largely to this quantity. TAS is important
for use in navigation (True airspeed ± windspeed = groundspeed)."


Bottom line IAS/CAS isn't going to change much, or at all for stall speed with altitude unless there is a large static position error or mach related influence.
Light GA piston, nada. Jet at altitude and high mach, some but not huge in most aircraft.