Moreover, what's to say that U2 won't sell 4 million in its life time?
Remember UDF? What did it sell in its first 2 months? Around 1 million or less...yet in its lifetime it sold 2.5 million. It was famously a slow burner that continued to grow more than other titles due to word of mouth.
With UC2 already at 2.5 million, it'll no doubt reach near 4 million.
Why does a game have to sell 4 million in one month like MW or Halo to be considered a success? What about the games that continue to sell healthfully?
If the discussion is on absolute numbers then no. If the discussion is around cost/benefit then it matters because x months after release date the retail price won't be the same.
Another thing to bear in mind is that publishers aren't interested in games that turn a profit as crazy as that sounds. They are interested in publishing games that turn a LOT of profit.
They don't view a game that turned in 1 million in pure profit as an extra 1 million on their bank account, they view it as a game that failed to provide 10, 20, 50 million in pure profit.*
Of course, whether or not this has any bearing on U3, or any other game, depends on the budget for the game, how the dev/publisher contract is setup and if there are other more promising games that developer ought to be working on (in the eyes of the publisher).
* And btw, these values are completely arbitrary, any game that fails to turn in enough profit to pay for the *next* game in development could, in theory, be considered a commercial disappointment. With budgets between 18-20 something million like the recent article pointed out even a successful game from a gamer's point of view might not wield any more sequels because someone decided the IP didn't have potential for the Mega-Profit (tm).