I don't know if we will ever see a Third Edition... all the current data is so bullet specific.
Darn near every Bullet manufacturer has their own reloading manual, specifically geared towards their product.
Lee's data is good for a lot of generic bullets,. 40 180gr JHP,. 308 165gr SP... etc , and that is one of its great qualities.
But a lot of the art of reloading, is being replaced but the bullet manufacturer specific data... us ol' timers frequently see questions about this exact topic.
The last one I saw was about a 55gr bulk bullet with IMR 3031... the guy was flippant when no one would answer his poorly worded questions..... originally I had written a lengthy post answering each question as best I could, trying to help ..... but then realized I was trying to put 25+ years of reloading experience into 40 sentences, for someone that was unwilling to spend time learning... he wanted YOU to do it for him.
None of us mind helping, frankly most are eager to help...
Anyway I digress....
The Lee manual is full of great meaningful info and data.... but the vast majority of new reloaders want it all now. The computer age is changing how people learn.... and any full encompassing reloading manual , like the Lee has been to me, would have a heck of a time keeping up with the internet.
Don't get me wrong.... I would pre-order a copy right now if Lee suggested they were printing one.
Lymans current AR manual, is a good example how tough it is to make a fully encompassing manual... I think it has all sorts of excellent info, but I have heard quite a few comments about "I wish they had included "this" specific bullet, case, primer, powder load.
Also... the flavor of the month powder syndrome.... the constant introduction of new powders ( a good thing ) .... makes it hard for printed, all encompassing data to keep up. For the internet it is perfect. For books... it blows. There was a time .... when you could count all the available powders on you fingers and toes.... now you would be hard pressed to name them all.