This is already the case, blame the KDE4 team. You
cannot reconcile
the two: KDE4 apps use KDE4 libraries and cannot be separated from
KDE4.
Fortunately, they can run really smoothly on Trinity, but it can be a
little mess with $PATH, etc.
With the drawback that it will load both kdelibs3 and
kdelibs4 into
memory. If you have enough memory to accommodate the 2 versions of
kdelibs, you have probably enough memory to run KDE4.