Well we know the two purple Versas won't be used on the X66, given that citaro5284 has previously said that the articulated Mercedes Citaros are to be (temporarily) replaced by four corporate liveried vehicles in the existing fleet...

The S1 service is not commercially operated. It is ran under contract to intu, and as 8266 (along with 8261 - 8265) has recently been fitted with Euro 5 Eminox modifications, there would be no difference (other than a few seats) between allocating 8266 and a Versa, so I can't really see why they'd upgrade the S1?