I’m interested in this for sim racing (ACC and Automobilista 2) but is my 2070 Super going to have enough grunt to run it at the full 90hz?
ACC is going to be a challenge but with sufficiently low settings yes... it's just horrendously optimised. I have however played it at 72hz on my 2070S with some up sampling on the Quest with the appropriate tweaking of settings. With a full grid you will actually find the CPU is preventing you from hitting 90hz though as again it's just really poorly optimised.
Many run ACC at 45fps (tweak the settings so you maintain minimum 45fps at all times) and turn on smoothing/reprojection. Hitting 90hz is just so hard that it's generally better to admit defeat, turn up some settings for a better picture and accept a few little reprojection artefacts as the trade-off.
AMS2 will be much easier and you should be able to run that on the 2070S no problem, but you may have to make a few sacrifices on the settings again to make sure you are maintaining that 90hz.
Am I dreaming in thinking I can pre order one now and get it before Christmas?
Was going to upgrade my dads oculus for Christmas..
Unfortunately no one can answer that for you, HP really aren't being overly forthcoming with dates. I would say there is a chance, but certainly no guarantee... I think if you want it any time soon though you'll be waiting probably at least into january/february (total guess, but seems realistic enough) for it to reach general retail availability so pre-ordering is going to be the only way to get it any time soon.