Not So Great Expectations? Citi Predicts “Modest” Sales for Nexus One.

Google’s launch of the Nexus One may end up being a crucial point in the company’s history, but it’s not going to have much impact on its financials for quite a while.

To its credit, Google (GOOG) has never said otherwise. But Citigroup’s Mark Mahaney takes a stab at guesstimating exactly how many new phones the search giant will sell and what that means for its earnings. Answers: Not a lot and not much.

Specifically, Mahaney thinks Google might ship one million to three million phones in the first year, which could generate up to $1.6 billion in additional revenue, and perhaps another 55 cents in earnings per share. That’s about half the estimate from Douglas Anmuth of Barclays (BCS) earlier this month. Mahaney cites both Flurry’s modest first-week sales estimates as well as internal Citigroup (C) research, to support his numbers.

He also provides some interesting context via this table, which compares the first-year sales for Apple’s (AAPL) various iPhones, Palm’s (PALM) Pre and Pixi models, and Motorola’s (MOT) Droid, which of course uses Google’s Android OS, just like the Nexus One. Click to enlarge:

One sort-of throwaway point: Mahaney notes that any benefit the Nexus One generates for Google this year may end up balancing out the money it could lose if it leaves China.