In a media briefing earlier today, Sony announced a device called PS Vita TV, which almost immediately seems like a shot across the bow of OUYA's indie-centric ship.
I've read some comments along the lines of 'The final nail in the OUYA's coffin' or 'this is the OUYA's death knell', but I see it more as a wake up call to both OUYA, Inc and OUYA developers to step their game up (quality over quantity, in essence).
Originally, you could argue that the OUYA complimented the PS3 with features and software it didn't have. The PS3 excels with first party titles, but it doesn't have, say, a Twitch TV app - which is where the OUYA came in. You could watch some livestreams on your TV, and if some friends came over, you could play a few rounds of Bombsquad or Towerfall. Even use the same controllers.
Even though that can still exist, Sony attempting is covering all their bases - and reach a larger audience - with Vita TV. The Vita already has a respectable library of great games as well as growing number of independent titles, encroaching upon the OUYA's territory.
This is where OUYA will really have to improve upon their current areas of weakness. They won't be able to compete on a hardware level (Vita TV, essentially, is a condensed Playstation Vita), but they can compete with exclusives. The OUYA will need more games like That Dragon, Cancer or Soul Fjord to properly compete with Vita TV and prove itself valuable.
Just as Android tablets haven't killed the iPad, I don't think PS Vita TV will definitively kill the OUYA, but this is the first micro-console to really play on the same field as OUYA (Gamestick and MOJO are too similar, I consider them compatriots). It will be interesting to see who comes out on top - I wouldn't count the OUYA out just yet.