Earlier this year I was "upgraded" to PS due to an equipment swap from a three class (pre-refurb) A330-300 to an A330-900 that had PS. There was no fanfare, the seat map just swapped the day-of and I found my seat to be PS. This was before the soft product was any different, so we got the same meal and everything as we would have in C+.

Barring any operational changes like this, it's not going to happen.