WiiHD, no the tech is NOT there. Nintendo's already using the best of the same-design processor from Motorola, and even just a few upgrades to the current graphics chip design is only going to help so much.
All three consoles are using ATI and IBM to make their most important parts of their respective systems. In 5 years the two with HD qualities will have helped IBM and ATI to produce these types of chips at the cost range that Nintendo will want, in order to produce a WiiHD at sub $300 levels. Also, by then HD televisions will be the majority in US homes as well as Japan, so Nintendo will see that as a must.