NBC has a lot riding on THE VOICE. It's their only top 20 hit according to the Nielsen ratings, while CBS, FOX and ABC all manage a number of entries in the top 20. The formula of THE VOICE is meant to give NBC a hit show much on the order of AMERICAN IDOL, which does considerably better. AMERICAN IDOL's ratings top 25 million, while THE VOICE only tops 12 million viewers. But, by NBC's standards those are blockbuster numbers.
THE VOICE's formula varies a little from AMERICAN IDOL enough to be different. The two shows are decided different enough, although both are singing competition shows. NBC is just happy to have this hit, even if it's little more than a naked attempt to create it's own AMERICAN IDOL knockoff. Even critics agree THE VOICE is good entertainment.
Like nearly all new sensations, the ratings on THE VOICE will almost likely fall at some future point beyond this current season. But, you can expect THE VOICE to be back next season for sure, even if the ratings might be a little softer than this premiere season when the concept seems new and fresh.