I do not believe the L45 is replacing the L39, it is offering a different transmission option in that size machine.
I do not have the official Kubota position on this, but my understanding is
that the B26 replaced the B21, then the M59 replaced the L48, and now the
L45 replaces the L39. In each case, there was (and is) plenty of inventory
of the replaced units for sale for a while. One of our Kubota dealers on
TBN can give the official story.
At the World AG Expo, there was no L39 (or L48) there, of the 50+ tractors
on display. I wish I had seen a brochure as I would like to know if there are
weight and hyd flow diffs.
This photo is of the new floor arrangement, with rocker HST pedal. Too bad
they are keeping the right-foot brake arrangement.