If you were counting on playing Ghost Recon Online with your shiny new Wii U in a timely fashion, it ain't gonna happen: Ubisoft has issued a statement saying they're focusing entirely on the PC version for now, and as such, the Wii U version is "on hold".
Speculation would say Ubisoft is running into issues with Nintendo's hardware, but the game's producer Theo Sanders states this is not the case. Rather, it's a matter of resources.
“It’s not a reaction to anything specific happening to [Wii U]. It was a really fun, cool platform to develop for. But you realise once you launch an online service that it’s an all-consuming effort, so we really wanted to have all hands on deck. It was the same dev team working on both SKUs, and [we] really wanted to focus on doing the PC version right.”
"...[this] was purely based on the fact that we had one dev team working on both SKUs and it was an all-consuming effort with the PC launch. It’s tough launching an online game.”