To slightly rephrase most of the previous comments:

If the N900 with its current software and current hardware meets your needs and price range, then buy it.

If you are looking for software that doesn't exist yet to run on the N900, then wait until it is officially announced for the N900.

Don't buy on rumor. If you want a device that will run Meego or Maemo 6, don't buy the N900 until Nokia says that Meego or Maemo 6 will run on it.

If the N900 meets your needs and you buy it, nothing new might be added to it but if anything is added in the future it will be a positive.