Disc replacements are very new and still in the experimental phase. Disc replacement in the lumbar spine (low back) is possible but it's not being used for spondylolisthesis yet. There is still concern that whatever is causing the vertebral slippage won't be corrected by a disc implant.
It's possible the force of the vertebral movement and load on the spinal joints could loosen the disc implant. There's also some question about how well the implant and nearby bone would hold up.
Long-term results for use of the disc replacement in cases of disc degeneration are unknown. More studies are needed of this treatment idea before it use will be used for more complicated problems like spondylolisthesis.