Here's a post from Reece about it too.
"Alright, the cat is finally out of the bag on the table size thing so we can actually speak somewhat freely about it.
So, let me address a few things to clear it up a bit as some of you are already freaking out a bit or speculating wildly about the why of things here.
First: do you have to switch your table size? No. As they say in the article, it's not required if you want to stick to a 4x6' although it is good to know that 9th was designed to be played on a smaller surface and the missions areas many of you have seen were designed with that in mind. They still function on a 6x4' for sure, but I wanted to put that out there.
Second: why did GW do this? The answer is incredibly simple: it allows new players to build a table using Kill Team boards that easily fit into boxes. That's it. No conspiracy, a simple choice based on what they felt was best for accessibility to the game from a business perspective.
Third: did we at Frontline have any input on this choice? No. We have absolutely zero influence in or usually even knowledge of product development choices GW makes. We only give feedback on rules. We were pretty shocked when we learned about this ourselves but the choice was made and we had to keep our mouths shut due to our NDAs. It was not fun to be in our shoes but that’s the way it goes.
Fourth: will we be running our events on these new sized surfaces? Yes we will. Once I got over my shock and aversion to the idea, and I saw that it was much better for the long term logistics of event organization, I started to come around on it. You can fit a lot more people in the same space, you need less terrain and over time, it will make it a lot easier to get involved as a TO as the barrier to entry has been lowered."