To find the answer, first look again at;
http://cospilot.com/documents/Why%20...20Altitude.pdf
Then, assuming ISA, and that we discount any position and instrument errors, convert the 10,000' speeds to CAS/IAS by dividing by 1.1 or 1.2, depending on which rule of thumb you adhere to. (The TAS and CAS/IAS at sea level are, of course, the same )
The result is that the conversion from TAS to CAS/IAS more than compensates for the increase in TAS with altitude, and that the CAS/IAS for Vx, far from increasing with altitude, reduces slightly, whilst the CAS/IAS for Vy reduces more quickly, both speeds eventually converging at the absolute ceiling.
So the answer is....... 'It depends, but almost certainly not'
MJ
