The lack of HD is becoming more noticable as we come towards the end of the generation. The Wii wasn't top shelf tech when it released four years ago and now it's becoming more apparent. That being said, I would not buy a simple HD upgrade. At this point they should simply ride the wii out until their next console which they already said will be HD.
My prediction, Sony and MS will get in a cockfight over 3D as it's the upcoming tech in TVs just like HD was at the start of this gen. Nintendo said they would not adopt HD until there is at least a 30% adoption rate(I think that was the number they stated). At the start of the gen the rate was much lower then it is now, I know i didn't even have one until this year. Now we have a small adoption rate for 3D and the big tech companies are going to push that while Nintendo's next console holds back on this added cost for the much more commonly used feature of HD. Then the gen after that when 3D is highly adopted we'll see Nintendo adopt 3D. I think their strategy is obvious and smart, let the big companies with lots of money push a technology while you use alternate means to capture the market, then benefit from cheaper manufacturing of the same technology later.
