I think we will see the next handheld platform revealed at E3 2010 for release Christmas 2010. Its been five years now and Nintendo rarely breaks that cycle. Remember the GBA had the SP and Micro before the console was replaced. Now the DS has DS:Lite and DSi and now the new larger screen, if Nintendo sticks to their past marketing strategy then we will see the new handheld launch next Christmas.
Now the DS is still selling extremely well. Some would argue Nintendo might ride the DS's success a little longer. If they do choose to stick with the DS then I expect a new handheld to be unvieled alongside WiiHD at E3 2011! Can you imagine if WiiHD and the next handheld launched the same holiday season?
Of course I don't think Nintendo will launch the next handheld the same year as WiiHD. The handheld would take sales from the home platform and vice versa! So my best bet is Christmas 2010.
-JC7
"In God We Trust - In Games We Play " - Joel Reimer
