If anyone was going to wait for an update, I would think it would be for one with a larger 3D panel, that will presumably be priced the same or slightly more than the original model today.
It should be a given that there will be a hardware refresh within the first two years of the product cycle. The only question is whether you want to play the games now or not.
Frankly, I don't see much point in planning out video game purchases two years in advance; if you want one bad enough to do this, scrape together the means if you have to, or just buy one now if the purchase isn't a big deal.
Personally, the only reason I order now is on the chance that they become as difficult to find at retail as the DS lite was back when I was trying to buy a couple of them.
In a worst case scenario and one or both of them are still in the box after debut (since I don't plan on buying any old games on release just to play with my new toy) and I'm still waiting on those MGS and RE games to be released, I can just sell them to someone who wants them now.