Quick reply...

Yes, not everybody will carry both Pyra and Neo900. Unless he-she truly intends to replace laptop with Pyra, and phone with Neo900...

If somebody has fully working N900, and is happy with it, he will be more likely to get Pyra than new Neo900, because having both N900 and Neo900 means having two almost identical devices, in shape (form-factor) at least.

But, N900 is slowly aging. Just because it was manufactured long time ago, and even under ideal storing conditions it's not going to remain "like new". Small battery for time-date storage is going to discharge itself, slowly; so-called water damage is going to accumulate; I am not sure what else. And even more damage is going to accumulate for N900 which is being actively used.

Sooner or later, you have got to replace N900. With what? Neo900, right. Unless some manufacturer, accidentally, releases a suitable phone (slider Qwerty, stylus, resistive touch screen?... you can dream). And for Neo900 to be in your hand, you need to pre-order it, because there is no guarantee of a second batch being made. Not soon, at least.

Replacing N900 with Pyra is like replacing, I don't know, a bicycle with a motorcycle. Or something. Very similar, yet motorcycle is larger, more heavy, and does not give you the same flexibility. You can take a bike on a train; motorcycle, hardly.

It may be a major funds sink - for those who are not millionaires ;-) - but I consider it worth it. Some people enjoy cars, or motorcycles, or something; I prefer mobile phones, PDAs, or however they are called.

Best wishes.