...is good for both Juventus and Arsenal.
This is a canny move on Wenger's part, who's getting decent money for a player past his best and who's correct to rebuild Arsenal's leadership and culture while the younger players -- particularly Fabregas and Flamini -- are showing maturity ahead of schedule.
Wenger may already have Mahamadou Diarra (Lyon), Samir Nasri (Marseille) or Modeste M'Bami (PSG) lined up to fill in Viera's spot, if not Jermaine Jenas. But regardless of a "replacement" or not, he is smart to release Viera now and not later when Viera is in the midst of the midfield's understanding which would then need to be unwound.
Arsenal's clique of French-speaking players (Pires, Henry, Flamini, Cygan, Clichy, Lauren, Eboue, Toure') will be disrupted by the departure of the Captain at their center, and this may make the Highbury locker room more hospitable for Ashley Cole and the other non-French-speaking players. Cliques are debilitating to team spirit and performance; they reflect a failure of managment (on multiple levels) and we have heard about Arsenal's trouble here. A change of culture -- even a modest one -- would give Wenger (a Frenchman) credibility and influence across his whole squad, particularly where players may have felt excluded before. It may even be a significant enough reason for changing Viera out.
There are indications that Thierry Henry will now captain the side.