Buy when you have the money to afford it and the desire to have a new bike. Use of a new bike has a financial value in my opinion. I would not wait 6 months to save $600 if I thought I would really enjoy riding the new bike immediately.

On the other hand, if you are not of the same mindset as me, now when new models are arriving is not a bad time to pick up a deal. Spring won't necessarily be great as demand will be up as folks want to ride more once the nice weather comes back, so you might not get as great a deal. But if you feel you see a nice deal at any point in the year, why not go for it?