Yeah, but even 50 Initiate/Magic would run 12,200 Karma...
And that's assuming you never want to bind a spirit to long term service, quicken a spell, rebuild your Edge attribute after a few close calls, have other stats above 2s and 3s, learn to drive a car, speak english, etc.
Though in theory, un-capped magic can occur, in practice, you just need too much of the other stuff to live to see 50+ magic to reach it in any kind of sensible manner. Just think of how many different etiquette and language skills said IE needs to have lived until now:
Let's say he lived in Italy, from whenever BC to present, this gives us:
Caveman, Phoenician, Roman, Vandal, Visigoth, early Italian, middle-ages Italian, Renaissance Italian, Modern Italian, then English, if he's going to be involved at all in America.
That's just to ask for some water and food. If he's going to get around, add to that:
Riding, Pilot Chariot, Pilot Carriage (yes, they're different enough), Pilot Ground Craft. In Italy, he probably would need to get some Pilot Watercraft, too.
Now, if he wants to survive the fifth age (no magic):
Clubs, Blades, Archery, Exotic Ranged Weapon (flint-lock musket), Pistols
All of this also assumes he has no desire to enter the business world, or otherwise learn the plethora of ways he could make money and survive as anything other than a bandit in the woods, awaiting magic's return.
All that is a lot of karma. So yes, in theory, an IE could get to 100 Initiation and 100 Magic (or 50/50) in the 7000 years, but he wouldn't actually live long enough to do so without also learning the majority of the skills I've just laid out. Heck, I'd argue that he couldn't initiate or raise his Magic attribute during the 5th age at all, there's no magic or astral to tap into during this time, so even if he stored up the karma, he'd still have to spend the years doing little else but increasing his Initiation and Magic once the 6th Age began. Remember, each grade is said to take
months to obtain (SR4A, pg 198). This could easily translate into years, especially if the GM decides to peg time to difficulty and difficulty to initiation grade.
So, yes, it's theoretically possible to get your magic up to 50 or 100 (and, therefore, initiation up there, too), but even with an iE lifespan, there is too many other things you need to do to survive the no-magic era for it to be practical to get up there. 15, 20, maybe. But, how many years in a no-magic world will you go without something qualifying as an "adventure", how much more likely are you to spend years as a shipwright (whoops, more karma expenditures) or a monk in a monastery (again, more things to learn, more karma not going to magic / initiation) and earning no karma, than hunting down and slaying beasties in the wild and performing sufficiently crazy hijinks to qualify you for those karma points?