Agree partially... don't care much for the Halo part, but I am looking forward to seeing Wii Motion Plus used more as 'standard' in future games, basically if enough games start to support it then people will buy it but as it becomes more standard then the price should drop and / or it should start being bundled with Wii remotes.
There is no advantage to Nintendo manufacturing a Wii SP / HD as this will just confuse the market; however their next console will need to incorporate a controller that not only retains the capabilities of the Wii remote with motion plus in one unit but it will also need to do something more on top of this, either way it needs to be fully compatible with Wii software.
Wii Motion Plus' future looks good, it's just persuading enough people to buy it initially that's the problem, granted sales of Wii Sports Resort are / will continue to be good but it will take games like Red Steel 2 to truely convince some people that it is indeed the future and a necessary peripheral.