skeetlee,
The most popular cartridge and the current choice of the US team is 6.5-284. After the recent World Championship, consideration is being given to making a change to a 7mm cartridge to deliver 2900 fps with a 180gr bullet. Charles Ballard just won the F-O National Champ with a straight 284 Win and Jim Murphy placed second with a 7mm short mag, I think a Remington. So if you mean by dominate the performance on paper, there could be be a shift going on right now.
Your suggestion of a 260 Rem has less recoil and much better barrel life than the popular 6.5-284 at the price of lower velocity and somewhat greater wind drift. Those are probably good trade-offs if you're learning the game. A straight 284 has better wind performance, good barrel life and a lot more recoil than a 260 or 6.5-284. Not a popular choice for F-O, but sweet shooting with great accuracy, long barrel life, essentially no recoil and a great platform for developing your skills (especially wind reading) is the 6BR.
Don't pick your cartridge by what is "dominant". That set of compromises probably isn't best for someone new to the game. Pick the one that you think will best serve your development. I think the 260 (or the 6BR) would be a good choice for many folks.
Greg