I don't know if anyone has been privy to the license agreement, but I wouldn't assume that LoTRO shuts down whenever the license expires. This is purely speculation, but I would guess that the license is perpetual for already developed content and the license ending bars the development of any new content.

When someone makes a LoTRO movie they have to license the rights. Those rights have a term and the film has to be made within that term. When that term ends the filmmaker isn't barred from selling that film any longer, he is just barred from using the intellectual property for any other development.

My guess is that even if the license is not renewed Turbine can credibly state without lying that they will support LoTRO for years to come by keeping the existing content and servers running. If Helms Deep is profitable I'm sure Turbine will want to renew. If it isn't they may be better off ceasing new development but continuing to provide the existing content.