Yep, now hit me too after dodging the dreaded 789 on my January booking I see both VS7 and VS8 now seem to be swapped in to 789s on a daily basis with VS23 and VS 24 retaining the A350.
Previously it was 789 just two days a week on VS7&8 so fairly easy to avoid, unless I was booking Premium.
It is a little odd as I'd understood it was lack of A350s, previously, which restricted them making LA all A350s (and giving the LA-route certainty of the suites).
It does look as if the VS7/8 A350s have now swapped across to SFO to serve that route instead.

Oh well, with the demise of the SEA route late last week this hasn't been my greatest week with Virgin ... and just as BA seem to be waking up their A380s and expected to pop one on the LAX route.