The only reason the 360 wouldn't be around in 2010 is if Microsoft decided to discontinue it before then. The very fact that they've got games planned to come out in 2010 on the 360 (hell, Final Fantasy 13 will probably be a 2010 game) suggests that MS has a bit more of a long term strategy with the system than to cut it loose within the next 18 months.
In fact, they could afford more aggressive price drops, especially in the US, if they so wanted.
The 360 isn't doing great, but it's the worst time of the year for the system and all of its big games are due out in September and later. The system will struggle in July and August, then pick up sales significantly for the holiday season.
In the US, the 360 is still the cooler system to own.
The 360 is also still selling software like gangbusters. Sure, the attach ratio is helped dramatically by the low sales of the system, but it still does fantastic selling software.