That's already possible in WoW's new competitor Warhammer Online, in which it is essentially just as viable to level up to the cap in PvP as it is in PvE. The WoW devs are likely responding to the competition, knowing that they might lose big fans of PvP to WAR. In that vein, they're also ensuring that daily PvP quests are available from levels 10 - 80.
It's hard not to look at this as a good change. The only argument against it we can think of is that if a player levels from 10 - 80 entirely in the battlegrounds, he or she will not have the necessary experience to run instances and raids at later levels if a change of course is desired. But that seems like a fairly minor criticism of a long-needed addition to the game.