Your guess is as good as mine as to whether any such incentives will be offered. I do believe that the HifiMAN HE-400 was introduced towards the end of the year, and there was a $50 off incentive for those purchasers who were able to get in on the pre-order. But, I do think if we do see any such sales, it might involve combinations. HifiMAN could pair their HE-6 with their matching amp and provide a small discount. But, the prices of that rig would be a bit more than someone hunting for a bargain would be looking for.
Also, do keep in mind that HeadRomm
http://www.headphone.com does have a "B" stock section for headphones that were purchased, but returned within the period. So, they sell these headphones for a pretty good discount. The HE-400 comes up every now and then for about $339.00, which is quite a good price.
Finally, we might see something from Moon-Audio as they do feature sales at various times of the year, which can amount to about a 10% discount and HifiMAN is included in the discount. There are times when they offer the discount to headphones $399 and up, so the HE-400 would be included. But, at the moment, I see that their coupon only applies to headphones $499 and up. There is a restriction with the coupon that reflects the discount doesn't apply to Grado nor Audeze headphones.
* Edit. Here is the link for Moon-Audio. They are located in North Carolina.
http://www.moon-audio.com/