Well, for the most part, from what has been said and what has been shown in the game play videos the rules really have not changed much. The main changes I have seen have been in a new naming conventions for some of the abilities (with things like Precision instead of Offensive proficiency etc..) and a cleaner interpretation of the rules themselves. The core rules themselves have not changed at all.
As for the rest, we have updates to Motivations and Army Builds, but these do not change the core rules. I figure that except for some additional motivation tweaks, the rules are final.
At this point I figure they have another 4-6 weeks to complete testing on the Wave 3 infantry and additional specialists before they have to send everything out to get printed (based on getting everything back in time to ship for a May Delivery). Would be nice to have a hint on what the abilities of the extra units will be, and if there are additional units in the book that we have not even seen/heard about yet