The HD700 model is more than 5 years old... are they any chances to see a newer replacement coming soon? I still wait before proceeding on such purchase...
Honestly, I wouldn't expect a new version. Sennheiser has so far made many variations of the old-school HD580 (HD600, HD650, HD6XX, HD660S, and soon HD58X) all of similar design with some sonic differences. So to have they updated the HD800 to the HD800S but some may prefer the less expensive original HD800. With the HD700, it doesn't have the same enthusiast following, but it is still being sold to the general high-fidelity maket (many who neither care nor have time for our audio forums). Seeing Sennheiser's track record, they only release a handful of major iterations to their core headphones each decade and, in addition, they create a few unique one offs and I think the HD700 along with the HD630VB are such cases. So if you can get an HD700 for a good price, you can be pretty safe in knowing that it is still going to be a great headphone even if a new version was released - that new version may have some small changes but not enough to completely offset the value / quality of the original.