Well, since there is no Lightroom 6 as of today, you can't do this migration.
But, normally, when you upgrade to a newer version of Lightroom, the catalog from the earlier version of LR should be automatically upgraded for use in the newer version of LR. So you don't lose anything.
Thank you so much....
And someone rumored that it will be available from 03/20/2015 :-(
Still waiting. So eager to test how is the CUDA working on the dev. mod.
Stop listening to the rumors. They are a total waste of time.