FWIW, I think it may be just the other way around. There's a ton of activity surrounding LibreOffice development and the traffic and number of developers seem to grow week by week.
This is not to say that OOo is any less active; I don't know. But it seems to me that LO certainly won't be superseded by a change in direction (or licensing) of OOo at this point. I can imagine that a re-merger of the projects could be a remote possibility, if licensing and leadership issues were ironed out.
I guess "unnecessary" is in the eye of the beholder? Just my 2c.