Evidently the Yosemite public beta will be released tomorrow around 1PM PDT. Downloading could take a while as there will be hundreds of thousands of folks downloading tomorrow.
From Apple. But it is a Beta being released to allow the public help shake out the bugs. If you rely on your computer to work it would be unwise to install a non-final release operating system moments after it has been posted. Reverting back to an older OS in the event of problems is non trivial.
I loaded Yosemite beta last night. The only serious bug I found so far was in the keychain migration from Mavericks. I reported that to Apple. So far LR and plugins work just fine.
