After much experimentation and confirmation from the myeclipse forum, it seems pretty clear that if you myeclipse there is no upgrading spring ide. This quite sad, as the new spring editor with auto-completion is great.
This is a common issue with myeclipse. They package so many external projects at fixed release numbers in their release that even upgrading eclipse.org projects can break your whole installation.
Since myeclipse does not release very often, I've had to create a seperate eclipse installation with the 0.7 of WTP but no myeclipse just to be able to use the latest spring ide.
I remember seeing on the myeclipse forum Torsten (I think) informing myeclipse that a new version of spring ide was out. This was just before the 4.0 release. But myeclipse said that they made lots of mods to spring ide and wouldn't have time to upgrade. Myeclipse did say that they would contribute back fixes to spring ide. Did that happen?