The N900 has a future, its just that the market has not discovered the difference between a mobile tablet computer and a mobile detachable peripheral.
ALL: the iPhone and Windows mobile assumes a coexistence with a computer / laptop. Apple coined this a "ecosystem". The Android use Google advertising to fund the OS.
Now take Android first: It is the operators that own the network. The moment they discover a way of distributing adverts comparably as effective as Google, its the end of Google and Android revenues. Ericsson has acquired a large share in the companies that provides the location based advertising, and can offer their service as an Ericsson mobile application to the operator. Nokia is good at this and its not that difficult, they have most likely a similar platform ready.

The N900 and N9 use Linux and runs any application that you can compile on Linux. So, you can run Oracle and SAP, just modify the GUI. You can take the company payroll application, and leave it for Oracle to "replicate" and do "update in place" to synchronise: transmit the timesheet and expense reports, no need to use an FTP and a CSV intermediary file. No need to use a standard application, you can use the same company application. Balmer need not qualify nor does Apple have to approve of anything.

So the market will develop. Nokia has learned a lesson, they need not do a thing, just wait and every 3 years release new hardware.

My guess is that we will get an Ubuntu Notepad release, with Active Plasma as Window manager soon. KDE is the platform for developing Qt. If they then can make this using a plain vanilla Ubuntu / Kubuntu platform they will get that pool of applications.