It's like the plane just gets longer and longer every time I see it, lol.  I wonder if the roundel will be changed on all following fighters too, or if it's only a one-off design.  I know it's the PLA insignia, but the PLAAF has always used a different one up till now.  I thought it was hilarious when some discredited early J-20 photos based on the similarity between this lone star and the Soviet roundel.
EDIT:
Oooh, what's that hatch/panel they opened up?  And that's interesting.  The J-20 model is so different from what's flying now.