There is no chance. The policy is that whatever package the device ships with is there, stays there, and cannot be replaced by a package which is not part of the PR (to avoid situations like PR parts using Qt4.6 which they have not been tested with). In other words, you would still have a libqt4-core.rpm and a development libqt4-maemo5-core.rpm which would the be renamed to the first one in the next PR. It's not that a packaging system cannot make the upgrade path or restricts it - it's a Nokia QA policy collateral.