The errata is of somewhat questionable value, really. A lot of the stuff it fixed that needed fixing is a very obvious fix, while a lot of the other "fixes" are widely considered unnecessary. More importantly, the published errata is completely separate from the paid services of D&D Insider, anyone can access it and it's not even on the same page (last I checked, anyway). Furthermore, I doubt they'd pull it even if they pull everything else from the site - D&D 3.5 errata is still available as well, after all.
The real value of the online stuff is the wealth of material from the Dragon magazines. Those started being published exclusively to DDI members as .pdf files, so pulling the DDI content would mean all that extra content being pulled from the site. From what I hear, the amount of content has been lessening lately, but especially in 4e's beginning days and at the height of its popularity, Dragon magazines meant like three-four articles of new content a month. As oslecamo said, though, anyone with a lick of sense who actually paid for them has them saved. Furthermore, there's of course the usual back alley routes of getting at them.