Does usrmerge have to happen before uprgade from desalus to excalibur?

Or is that for the next bug upgrade after excalibur?

I currently have separate partitions for / and for /usr.

Will /usr still be a separate partition from / ?

Should I repartition so that /usr has at least as much free space
as / currently has occupied space? Presumably it will have to be able
to get a copy of everything from /bin, /sbin, and /lib.

Or should I preemtively move everything in now in the /usr
partition into a new /usr file tree within / , thereby
abolishing the separate /usr partition?

-- hendrik