I expect haste to play a large part in the talents for mana regen as you get more haste in the mastery bonus. Making you run out of gas faster without compensation for refilling would be bad design and I'm sure they'd avoid that.
Im sure we will see a talent in the arcane tree being X amount of mana return for X haste, seeing as how the mastery alone grants more haste, and now fire spec and frost spec have haste bonuses, one being IV and the other being Pyromaniac. The "haste" direction has a few different openings in all trees now and it seems to be what blizz is focusing on as the main point in arcane.
And if this were the case, where mana regeneration was controlled by haste for arcane, then the arcane tree would truly be a haste dependent spec for the pure reason that if you have more haste you would pull higher DPS because your mana pool will constantly be regenerated. And as side effect because of your mana regeneration rate you DPS over a longer fight would be substantial higher, unlike how arcane drops with CD's on now. Basically meaning, the bigger and better gear with haste you have, the higher DPS you do because of high mana regeneration.
The rotation then wouldnt be so hard. It would simply be adjusting to your mana regeneration in adjacent to DPM, then your gear would determine not only how much damage you do from a SP and Int basis, but also your mana bar being as close to 100% as possible though haste.
If this were the approach to the arcane tree that blizz had intended, I would love that. Having my gear with int, crit, gems, and haste, with haste being the big part of the gear, determine how much DPS I will pull..... I can get used to that most definitely.