Chances of these games being playable on the Switch? Don't have a Wii U but want to take advantage of the offer and get Wind Waker HD on my account to play at some stage on the Switch.
Like cross-buy? Very unlikely. I think cross-buy has only ever been a thing for eShop games. Virtual Console games have gotten large discounts when activating the license on a new console, but this wouldn't count as a Virtual Console game as it'd likely be impossible for Switch to emulate Wii U at this stage.
If WWHD comes to Switch, it'd have to be ported over. For that reason, I could see it being bundled with something like TPHD and sold at $40-$60. Because it'd have to be a port made after the original development, I would expect Nintendo to charge for the new versions. I would not count on any Wii U game licenses transferring to Switch beyond maybe VC titles. With eShop games, we're already seeing developers charge prices for Switch ports (Shovel Knight, the Tomorrow Corporation games, etc.), so I'm doubtful we'll see any cross-buy between Switch and older hardware. Look at MK8D as an example of how Nintendo will likely handle Wii U ports. Actually, for the best example, look at Breath of the Wild.
(For the record, I expect a new view of license ownership with Switch and the new account system, so I think we could see what you're suggesting going forward. However, I do not expect that to extend backwards to Wii U beyond maaaybe VC games.)