It's not an "announcement". Quite the opposite: Nokia has explicitly denied FTD's report that they would be abandoning Symbian. However, phones equipped with Maemo 5 are definitely coming to the high end of Nokia's range. (Symbian's strength is that it works with substantially cheaper hardware than any of the competing smartphone OSs, which is great for Nokia, as they are particularly strong globally at the lower end of the market and in emerging markets.)
The important point is that Nokia is adopting the Qt toolkit across the range. Both Symbian and Maemo will have Qt at the top of the stack by 2011. At that point, the underlying operating system won't be particularly relevant to application developers anymore: C++ software written to Qt (with the upcoming Orbit touch UI framework) will be just a recompile away from being ported to Symbian.
The important point is that Nokia is adopting the Qt toolkit across the range. Both Symbian and Maemo will have Qt at the top of the stack by 2011. At that point, the underlying operating system won't be particularly relevant to application developers anymore: C++ software written to Qt (with the upcoming Orbit touch UI framework) will be just a recompile away from being ported to Symbian.