Some good points made but all we know for sure is that both teams are working, thats it. I fully expect the new zelda to be radically different from TP so that is gonna take some time. How much time? Well lets speculate a little.....
Zelda TP came out at the end of 2006 after 4 years of development, so lets say the ground work for the new zelda started early 2007..thats exactly 2 years ago. Phantom hourglass doesnt matter as it was a side project for the zelda team. By the end of this year it would be at nearly 3 years in development (bare minimum development time for a main zelda project).
My prediction is we could very well see the new zelda trailer at this years E3 followed by a late 2010 release date, probably Q3 2010 or as early as summer .
As for mario it all depends on what they want to do with it. If its a straight sequel to galaxy then development time should be minimal(approx. 2 years) so in this scenario expect a new mario by end of this year(xmas 2009). However this is nintendo we are talking about,they love to surprise so anything is possible, even a completely new direction on the mario franchise. The only sure fact is that E3 should be something special this year..here is to hoping.
My speculated prediction for both titles is;
New mario Q3 2009
New zelda Q2/Q3 2010







