This. People are really naive if they think that just because logins carry over it means that content will as well. It all hinges on whether or not the PS4 and 720 are fully backwards compatible with this gen or not. If retail games don't work on next gen consoles, then what magic do they think will make DD games work?
It's ironic that Wiiware is the most likely to transfer, because the Wii U is the only next gen system guaranteed to be backwards compatible so it's only a matter of Nintendo setting up a transfer app that logs into whatever account system they come up for the Wii U and removes the licenses from the Wii.
Sony and Microsoft already have cross-platform account systems, but it means nothing if their next-gen consoles are unable of running previous-gen code.
I'm sure the big 3 see DD and retail games the same: content you purchase to play on the console it was programmed for. Whether or not the games play on any future hardware is dependent on if they see the hassle of BC as worth it or not. Since Nintendo has already confirmed full Wii BC, theoretically they could release an update that allows you to tie your Wii to a specific Wii U account and enables re-downloads that way. Whether or not they will is another story. As for the other 2, we'll just have to wait and see what the BC situation is like.