Have a look at the "MORE LIKE THIS" on the right hand side of the topic.
In short there is a ACR 8.6RC that will open only large RAW files but it is only for Photoshop CS6/CC.
There is a DNG Converter v8.6 RC that will convert NEF to DNG so you can open in Lightroom v5.5
Otherwise we expect there will be a Lightroom v5.6 release before 31 August.
LR 5.6 is available.