Neversoft has announced that the Guitar Hero World Tour drum set will finally be available as a standalone product beginning February 15. The drums will come at a price of $100 -- $10 more than the Rock Band 2 drums -- and will be available at Best Buy and GameStop. Unfortunately, this only applies to North America, as Neversoft notes the drums will arrive in Europe and Australia "at a later date."
While the World Tour drums are more expensive than the base Rock Band 2 set, it's worth noting that adding the cymbal expansions to Rock Band 2's set makes them slightly more expensive. Taking a look at Amazon (with prices lower than retail), the Rock Band 2 set with a two-cymbal expansion amounts to $107.92.
Be sure to check out Joystiq's Instrument Compatibility Matrix if you plan to pick up a set.