Keith,
I wouldn't say it's dead. But if your going to build a sporter weight long range rig with a longer barrel on it, consider the Winchester action has a smaller tenon thread diameter than the Remington and I beleive it's shorter also. Plus I've heard some 'smiths say they lean away from Win actions when using 404 case head chamberings due to the smaller diameter steel around the chamber as compared to the larger tenon thread diameter of a Remington or any of the really big custome actions. This is the same as some 'smiths will not built a 338 Lapua or 378 Weatherby on a Remington as they don't think there's enough of a safety factor built into them with that diameter of a case head. But they will built a 404 case head chamber on a Remington in a heart beat.
Then accessories that are available to true up and add on to a Remington make the Winchester action very cost prohibitive and your not going to end up any better than a Remington. Me personally I don't care for the way gas could escape in the event of a total case head failure on a Winchester, but the Winchester safety that truely stops the hammer from going forward when engaged is light years ahead of the Remington's so called "safety" that might stop the trigger from being pulled but it has nothing to stop the hammer from going forward. A little perosnal opinion thrown in there for what you think it's worth.
BUT... with that said, if you build a rifle that the barrel will be barrel blocked then the tenon thread diameter/length issues go out the window. The reigning IBS 1000yd Shooter-of-the-Year uses a M70 action on his blocked HG. So when you do this the action goes from being the foundation of a rifle that everything is connected to, to simply a place to hang your trigger and load the chamber with nothing else touching it. I hate shooting against that rifle! M70 action or not. It shoots!!
Hope this helps,
Steve