Bike technology is really pushing XC riders' abilities and XC race course design. I feel, especially at the higher levels, XC course design is behind the curve. No pro should be able to win a World Cup or NORBA XC race on a hardtail. Yet, course designs remain virtually unchanged from year-to-year without regard to improved bikes.
FR, on the other hand, has no rules, and, perhaps, the most appealing aspect of all is the ability to FR in town, at parks and in the urban landscape. Hucking and drops can be found without schlepping out - maybe hours - to your local wilderness trailhead or DH mountain. The urban market opens "mountainbiking" up to many, many more people than the pure XC market.
Furthermore, FR forces technology to catch up to it, and doesn't have to cater to the whims of the UCI or NORBA. Do your own thing, dude!
I see the practical advantages of FR, but confess my devotion to XC riding/racing. Yes, my desire for technical singletrack crosses to FR, but ultimately I want a bike I can ride for hours on one weekend and race at a high level the next. I ride a Giant NRS and will never go back to a hardtail. It's not a bike for big drops, but it climbs like a fiend and descends faster than my old hardtail ever thought.
FR is here to stay for riders that don't want to DH, or simply can't because of geography, or whatever reason you choose. However, XC is the core of the mountainbiking as most riders start here.
Now, go ride!