Hmmm... I reviewed the stadium as it stands (according to a sketchup warehouse model that seems to be very close to the pictures I could find, the 2010 original poster's proposal, and the youtube video of the new design (https://www.youtube.com/watch?v=bza_mEkYALg).
I do see some similarities. It especially seems that both the 2010 proposal and the new design seem to pull the end seats closer to the field, but there are significant differences, also. For instance, the 2010 proposal uses the existing building basically as is, replacing the roof over it. The new design significantly adds to the building. Also, some of the "design elements" highlighted in the original pictures are actually what the stadium looks like now, and both the 2010 proposal and the new design utilize them.
http://www.dcyale.com/s01.jpg
I would be surprised if the person or persons doing the schematic design didn't see the 2010 proposal, but there is a lot of work that was done. The roof lines are very similar, but that seems to be more a matter of form following function.
It looks like there has been some engineering for the new design roof, and the new design uses a different support system.
http://www.dcyale.com/s02.jpg
Most strikingly the interior has a much different look:
http://www.dcyale.com/s03.jpg
The pillar spacing seems to be the same, but I am not sure if that is a function of design or engineering.
So, in my opinion, while some areas seem to be inspired by the 2010 proposal that was in the warehouse, the new proposal has significant differences and seems to have a lot more engineering in the roof supports. I suspect that the similarities that do exist are functional, not design, and probably would not support a legal action. Of course, the laws in Europe may differ significantly from the laws in the US, and that might make a difference.