Thats just a warning. Apparently Mojave is last OS that will support 32 bit apps. As far as Lr6 being updated, it will NOT be updated for any issues.
You also should be aware the Map module quit working Nov 30 in all versions of Lr before Lr 8
I received a warning notification when I started Lightroom 6 standalone version yesterday. The message says that the application needs to be converted to a 64bit app to work with the next release of Mac OS. I only recently purchased this software and did so because I don't want to pay for a CC subscription for a bunch of applications that I don't use.
Is Adobe going to update Lightroom 6 standalone version to a 64 bit app? If not, how do I get my money back as I'm not prepared to run old operating system versions to support legacy software apps.
If you are prepared to pay money for legacy software, then you must also be prepared to run a legacy operating system.