There is a very high probability (no doubt) that Apple will indeed make use the existing infrastructure and re-brand/re-develope Beats into their own. However Apple could have bought any other headphone manufacturer and do what you hypothesize. Why do they 'need' Beats? Marketing. If not for the headphones, for Dre and Iovine. Apple could literally hire the best of the best from anywhere in the world who have the same skills and knowledge as those two. But will they be as 'cool' as Dre and Iovine? Me thinks not. But that's just my 2 cents.
this is going to sound rude but it's truth... both apple and Beats are social statements, and both of them are... hugely popular with consumers. I think Apple plans to use the existing success that Beats had and take it to the next level, we all remember how tacky some of us where in High School... well we can think of Beats time with Dr Dre as a "high School run" he got hugely popular but now that Beats is under Apples name... it's like when you went to College... what ever made you cool in High School... might have gotten replaced by what may now allow
Maturity, why build a new brand when you can enhance and mature an existing one, you know? Some one else has already done the ground work, now your purchase that base and build off of it. saves time and money
Apple won't try to be "cool" with the Beats name, they are going to aim to mature the brand and hopefully get the consumers who bought into the "cool" factor of beats to mature with the brand they love, I think Apple Wants to ReBoot the beats name, take all of their previous customers and get some new ones