[identity profile] johnbobshaun.livejournal.com 2008-07-17 02:38 pm (UTC)(link)
"So far as I understand so far it's not going to be standard - it's going to be an addon"

http://www.eurogamer.net/article.php?article_id=190125

"Apparently Nintendo can't decide if MotionPlus should be integral to Wii remotes, or if "it might be good to keep it as an attachment we only use for certain software".

Aside from that, yeah you're probably right. I'd be surprised if it's used in more than a handful of first party titles though.