That's correct - the 4S is the true replacement for the PSS.
According the guy I spoke to at Michelin also told me that the current 4's will outperform the PSS's in 99% of situations. The last 1% will be at maximum balls out at the very limit of adhesion on track situations.
Guy I spoke to recently said that the Sport 4 wasn't a replacement for the Super Sport.
I have run Super Sports on MK2 LCR Stage2+ and MK3 Cupra 280 Stage2.