i don't think hardtails will become obsolete. The new FS bikes coming out (the specialized - studying your MTB mag eh? hehe) are not cheap. For a similar priced FS, you can still get a HT w/ lighter weight and better parts spec. It's all about how much you can afford to pay. If you want an FSXC bike that is race-worthy (ie: light weight) you'll be paying a fortune for it, only to have it weight 23lbs. Then you'll have to dump a fortune on it to get it bellow 22lbs, if the frame is light enough...For a HT, you can get a light bike that can be raced, and without going anywhere near the price of a fully lightened FSXC, can still make it lighter than 22lbs. For some people, weight is one of the highest concerns for XC riding/racing. This is where the HT is tough to beat.
In my opinion though...if i bought a FS bike, i wouldn't see a reason to have a lockout if the design of the suspension was efficient.
peace