I just don't want to have to go through a bunch of boring quests for the ability to create custom spells.
I didn't like that either, but not being able to ceate custom enchantments bothered me even more, because whereas only magic using characters who I'd likely join the Mages Guild with anyway can benefit from custom spells, any character can use enchantments, and yer for my non-magic using characters, it doesn't make sense to join the Mages Guild.
It's not a retcon because it didn't change anything that happened before. Everything that the guild did in the past remains completely untouched. Things just change as they move forward.. it's natural progression.
Indeed, this kind of thing changes over time. The Mages Guild we all remember may have been around throughout the series, but that doesn't mean it must remain so in the future, especially since there's already been lots of other changes with the Empire collapsing and Morrowind getting destroyed, and two hundred years passing since the last game, a good part of which still hasn't been covered, leaving much room for other things to happen we don't know about yet. Things change over time, this is true in real life, and there's no reason it shouldn't be true in fiction as well, and if the first few decades is any indication, the Fourth Era has brought many changes to Tamriel.
Myself, as long as there's some form of mage organization, I don't mind if it's a different one from the one we're used to, the Mages Guild was a little on the generic side anyway, when you get down to it. It's pretty much what it's name suggests, a guild of mages. I don't really have a serious problem with that, but replacing the old Guild with something new may allow Bethesda to do something more interesting.
All in all, I doubt they included the part about the Mages Guild splitting just to have things go back to the way they were before, so maybe we will see both factions, or maybe only one will be present in Skyrim, but I think we can assume, at least, that there will be a magic oriented faction in the game, and it probably will be a little different from the Mages Guild we're used to.