You understand it right. However it is not ready yet - Tungsten's work on Gallium is work in progress and CELL OpenGL renderer is not yet complete (AFAIK). If it was, it should be possible to port PS2 emulator (or almost any other emulator) to Linux running on PS3. Also I think most of the PS2 emulators are coded for Windows which would make this task more complicated but not impossible. The main setback for (Linux) PS3 gaining various nice stuff is lack of accelerated graphics - in Linux hypervisor blocks direct access to 3D features of the GPU.