I haven't been following an awful lot of this - is the January hearing a new thing?
What happens in the meantime, does this potentially mean (aside from the obvious stress and anxiety caused by an impending trial, of course) that the pressure is off and some of the previous stress and financial burden is relieved?
Unfortunately, no. The cost is likely only going to increase as they need to prepare for trial. I've never worked in the US system or on large commercial/IP disputes, but when I've represented clients in the courts in Scotland, the amount of work done just before the trial is much greater than anything done before (when you are mainly shuffling letters and paperwork about, and appearing for short periods of time). You need to organise and prepare all of your evidence (normally trying to agree a bundle with the other side, to simplify things as well), prepare questions for your witnesses, have all the research and precedents to support your legal arguments, understand what arguments the other side will use and what they will ask witnesses and be prepared to counter that etc. - it's an awful lot of work! You literally need to be prepared for anything - everything that's gone before then is always much more narrow, and thus preparation is much simpler. For letters that are going back and forth, you've always got plenty of time to research if needed and then respond. Not so in court for the trial!
The good thing for Kier and Ashley is that they wouldn't need to be that involved in all that, which would hopefully let them focus more on xenForo development in the interim period.
That said, I'm also slightly worried based on statements at vBulletin and activity here, that a settlement is in the works... June 12th could be an interesting day.