The decision to switch completely to a Fedora/RPM based distribution is a very bad idea, especially for ARM based devices. Debian/Ubuntu has officially supported ARM ports of the distribution for years, while Fedora is still struggling http://arm.koji.fedoraproject.org/pa..._be_fixed.html and not officially supporting it.
Moblin has nothing to loose from the merger, but Maemo will loose access to relatively easy ARM ports of Debian software (cf. Jebba etch port)
and reasonable Debian standards.
The package format themselves may not be very different, but the infrastructure and the available software differs a lot.
Debian and Ubuntu are LSB compliant and can install rpm packages using alien but LSB does NOT require the whole distribution to be based on RPM or Fedora!