I don't think Disney will tone down Marvel, just look at Disney owned Touchtone Pictures for example. They've operated TP for years to make mature and adult films like: "Rushmore," O Brother Where Art Thou?," and the forthcoming "Surrogates."
What I find amazing is that a company with such a wide reach and so desperate to stay on the top of the mountain would stake 4 BILLION dollars on a collection of characters that have been ludicrously milked of their usefulness as of late. (Last I heard Marvel Studios was considering making "Werewolf By Night" into a film - clearly they're out of intellectual properties to franchise.) This deal seems VERY sweet for Marvel, but I believe Disney bought way too high and will only see their investment depreciate - especially in this volatile world economy.
The only reasoning I can think of for the buyout is that Disney wants an easy paycheck. They can sit back and just collect all the fees, residuals, and licensing money made from "Spiderman the Backpack," "Cyclops the Can Opener," and the "Official Dazzler and Speedball Wastes of Money," all while never having to lift a finger.
As for the comics, I REALLY doubt that someone will prance into Marvel's NY office and declare, "Well, I never have read any of these 'Comic-ed Books,' but I don't think children need to see this half naked man with the fist-knives stabbing people. What if some child tried to recreate Mr Fist-knives here? Hmmm? Well, we won't have that anymore! Let's replace him with a cleaner cut young teen named 'Wolvy' who loves to rock-and-roll and to obey his parents! Now, let's go make these novels less graphic!"
Disney knows better than to kill their cash cow when it's still got quarters falling from it's money teats.