Relicensing Linux is practically impossible. Because there were contribution
from tens (hundreds?) thousands of developers and no copyright assignment,
there are as many copyright holders. Each of them should explicitly agree to
any relicensing.
But, yes, Linux Torvalds himself said he wants hardware vendors to be able to
ship devices with his kernel and the technical impossibility (enforced by
hardware restrictions) to run modified versions. In this context, the GPLv2
can be respected even if the freedom to modify the software is blocked in
practice. GPLv3 prohibits this practice known as tivoization.
Other famous Linux developers, such as Alan Cox, see the GNU GPLv3 as an
improvement over the previous version.
