Francois, if it would only take 3 weeks, I would strongly urge you to give it a go. I am a massive fan of click team products, have been since I was a kid, and I am now using it professionally to start up my own business. They’re great products. Let's for a second not talk about just current user's of Clickteam product's, but think about the Clickteam brand as a whole and potential new customers.
There are likely to be people out there who, when looking at a product such as Fusion, will see what platforms are supported and when they see that you do not support something like Wii U but a competitor does, the chance of you losing that customer will dramatically increase. Since Scirra supports Wii U, there are a lot of customers you might lose soley for that reason.
If Fusion had exporters built in to them for all of the major consoles, your potential to increase your market share will dramatically increase.
Let's talk about Unity. From what I understand, Unity is becoming and has become the game developers tool of choice for creating games for Wii U and I believe also Play Station and X Box as well. Why? 2 reasons - because it's awesome at what it does, and because it supports those platforms. Fusion doesn't even have a chance of being say the 2D game creation software for those platforms at the moment, because it doesn't support them. Imagine if you did. The more platforms you support, the more chance there is that Fusion becomes the go to program for indie developers making 2D games.
Granted Wii U has a comparably small market share compared to the other consoles, but that's the wrong way to look at it (and btw, it has over 3.9 million Wii U’s sold worldwide – while that’s smaller than other platforms, that’s a heck of a lot of people to sell to in reality). We need to start out with the bigger picture in mind - dominating the market in terms of being the game creation tool for 2D games for all platforms. Also, if you achieve that, you are more likely to sell any of the exporters you create.