I really doubt they've been *actively* developing the game since 2006. I remember those rumours that said a new Zelda was in development since before TP came out, and I do belive those rumours were later debunked as false, Nintendo needed all the time and resources they could get to get TP finished and out on time.
I could see how they would've started development on the new title sometime shortly after TP came out, but that would imo probably have been pre-production processes, like Rubang said...
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