From Sasler and qgil last posts I did some research and came to some conclusions that sound like a conspiracy theory, but anyway seemed to me a possible strategy from Nokia which would make sense...

These are the know facts until now:
- Nokia extensively advertised that Qt is strategic due to platform independence, and its implementation would ease a lot the portability between Symbian and Maemo, or even other O.S. like Windows Mobile, provided that all use Qt libraries.
- Qt 4.6 for Maemo is in beta stage and should be supported officially by the next firmware update PR1.2, which is rumored to be release by March/April
- Maemo developers are being instructed to focus their development on Qt to avoid incompatibility on Harmattan
- Ovi Maps 3.03 for Symbian was only made available for mobiles running S60 fp3 and fp5 editions, and its graphical interface changed considerably since the last edition.
- Qt 4.6 for Symbian is available only for S60 fp3 and fp5, and some features from Qt like Kinetic scrolling were implemented on Nokia 5800 for example.

Now the conspiracy part:
- I believe Ovi Maps 3.03 for Symbian is based on Qt, but couldn't find details about its code. It may be a coincidence, but now it is only available for devices which have support for Qt4.6
- If the above assumption is true, really wouldn't make sense to invest in the current Ovi Maps for Maemo, which most likely is not based on Qt since it wasn't officially supported at N900 launch
- When N900 gets official support Qt4.6 it will be much easier porting applications for Symbian already based on Qt, and that could include Ovi Maps 3.03
- I asked Nokia USA customer care and they told me that free turn-by-turn navigation will be offered soon for N900, not Maemo 6/Harmattan. I am not sure if the guy really had this confirmation or made some mistake, but anyway here is the email:
================================================== ===
From nokiausa.customercare@nokia.com
Sent: Tue, 2 Feb 2010, 14:33:48 BRST
To my_email@gmail.com
Subject RE: Phone Features

> Hi Alex,
>
> Thank you for e-mailing the Nokia Care Contact Center. We are glad that you are
> interested in the Nokia N900
> Based on your concern, the voice guided navigation on the N900 is currently not
> yet availble though it will be offered soon. For future updates regarding this
> matter, you can visit our website through www.nokia.com. I hope the
> information provided proves useful.
> If you have any additional question, please don't hesitate to contact us again.
> To ensure proper handling of your case, kindly continue using the current
> subject line Thank you very much for your email. Have a great day.
>
>
> Best Regards,
>
> Mark Bañas
> Email Specialist
> Nokia Inc.
> [THREAD ID:1-4XBUE4I]
================================================== ===

It would like to hear from you if I am going crazy or there could be some logic behind these assumptions....