I tried my hand at estimating their parameter count from extrapolating their LAMBADA figures, assuming they all trained on Chinchilla law: https://pbs.twimg.com/media/Fvy4xNkXgAEDF_D?format=jpg&name=...
If the extrapolation is not too flawed, it looks like PaLM 2-S might be about 120B, PaLM 2-M 180B, PaLM 2-L 280B.
Still, I would expect GPT-4 trained for way longer than Chinchilla, so it could be smaller than even PaLM 2-S.