Theories as to why we haven't heard anything regarding Pokemon Z yet?

If you look at the release timeline of Pokemon games, new games come out roughly every 1 to 2 years. With the gap between a new gen and its 'third version' never being more than two years. Its now been over two years since the release of X/Y, with no word of a Pokemon Z.

In addition to the bigger time gap, there are other unique factors to consider. Such as showing a new Pokemon (Magearna) before announcing a 'third version', a Nintendo Direct focusing on Pokemon this week and it being Pokemon's 20th anniversary.

Is Nintendo planning something special for Z that takes more time to develop? Maybe (finally) a home console version? I think if Nintendo ever wanted to do a home console version it would be a 'third version'. I expect they want to keep launching new gens purely on handheld and any console version would be a spin off.

What are your theories?