I'm going to say yes. Not because of Ovi Maps necessarily but because it was more or less confirmed that Maemo 6 will not be coming to the N900.

Without Maemo 6 the N900 has no future.. since many things are being worked on for maemo 6 and not 5.. even current feature requests or bug reports.

So anyone buying an N900 today is effectively planning to be on their own in a short while.