Mages are going through some pretty significant changes, though some argue rotations aren't that much different. I say, "Ha!"
Although Fire mages, which is proving to be by far the most exciting tree in the class in Cataclysm, has a much more dynamtic approach to fighting than it has before. With such spells as Improved Scourch and Improved Flamestrike, mages will be burning everything in sight while on the move. Not many classes can boast cast-as-you-go flexibility, but Fire Mages not only get a full array of spells that allow movement, it does insane AoE DPS. Proof below:
Cataclysm Beta - Fire AoE Madness + Flame Orb!
I've read that the new Fire Orb isn't living up to expectations, but the other changes have demonstrated amazing results (see Elitist Jerk's spoiler at the bottom of the first post here for Spell Coefficients). However, there are issues to take into consideration especially when running with a group:
1) CC involved pulls break when AoEs are used.
2) Hot streak doesn't proc as often as it does now.
3) Mana efficiency is a major issue currently in the patch (which isn't expected to change much when it goes live).
4) Fire has too much emphasis on DoTs and AoE.
The debate is pretty hot and heavy at Elitist Jerks, bringing up burning issues such as boss encounters in raids where single target DPS is lacking in Fire, the lack of Fire Streak procs, and issues with Combustion. Arcane may prove to be the winner for single target, but given its complex rotation we could see more go Frost on the duel spec. Indeed, Frost is taking an interesting turn boasting higher coefficients than fire on EJ's number-crunching charts. So it might be one of those things where a mage goes back and forth, which isn't much different now for heroic modes in ICC, but something to consider based on playstyle, group composition and boss strategies.
I can tell you this, I'll be at the dummies for a while to determine the best build and rotation until I determine the best of both to maximize my DPS. I'm certainly no min-maxer, but like any other girl I'm all about whats muy caliente.