I've seen nothing to even hint that Nokia shelved plans to release and fully support Maemo 6 on the N900 due to the merger into MeeGo. I don't believe such a plan ever existed.

Beyond the codename itself, little information about Harmattan was public prior to Maemo Summit 2008. It was at that Summit, when community developers were just getting information on the general architecture of Fremantle for the first time, that Nokia began talking about Harmattan as the great thing that lay beyond.

That 2008 Summit also marked a peak in community frustration with Nokia. The announcement that Fremantle wouldn't be made available for N8x0 devices hit hard, and a few good developers, important enough to be brought to the Summit on Nokia's dime, left in disgust. Had Nokia plans to bring Harmattan to the upcoming "Maemo 5 lead device", that would have been a good time to do it. "With the Internet Tablets, we've been leaving old devices behind when the next big thing arrives. Due to a performance jump and a lack of cellular data hardware, we're forced to do that again with Fremantle. Sorry. We've learned though, and it won't be happening again. Maemo 5 devices will be upgradable to Harmattan." Nope.

By Maemo Summit 2009, MeeGo talks with Intel must have been underway, but that wasn't announced. A few details of the Harmattan hardware platform were announced though, and overall, they sounded quite similar to the N900s that were handed out--except for the shift to a capacitive, multitouch display. Was it, "Don't worry though, the Harmattan UI is fully usable without multitouch, and an upgrade will be available for the N900"? Nope. Paraphrasing, it was: "Supporting both resistive single-touch and capacitive multitouch would be hard in a UI."

The MeeGo announcement didn't doom the N900. MeeGo just put a new, shiny coat of paint on the already approaching Harmattan release to make it more noticeable. Good or bad, what was, is, just under a new name.

If anything, the merger to MeeGo and corresponding tie to the Linux Foundation may benefit the N900, but that's another discussion.