Here's text from his TV interview, and for Spanish speakers, the 15 minute video. The news is that he's meeting with the Competition Committee Friday to turn everything over, and Sunday he'll go to the team camp for two weeks of normalcy.
http://www.biciciclismo.com/cas/site/noticias-ficha.asp?id=33003
http://www.rtve.es/deportes/20101125/contador-espero-resolucion-favorable/375747.shtml
I don't think the excerpt got his reply right about if he'd retire if banned. He wasn't making a threat to try to influence a decision.
http://www.as.com/ciclismo/articulo/sancionan-anos-seguire/20101126dasdaicic_1/Tes
As to the why he would retire, I've answered before, but here goes. A two year ban would have him miss all of 2011, and he could only be back for the Vuelta in 2012. If they take away his 2010 Tour win, why should he train for a couple of years with no salary just to try to win a third Tour AGAIN in 2013?
He's already won the races that matter to him. He's got millions of dollars, but he still lives a quiet life (with nice cars). If he walks away from the sport, he can go on with a life with no reports, or people knocking on the door every couple of days asking for blood or urine.
Look at some of the posts and threads against him here. Look back at the way the UCI treated him, with a gag order for more than a month so he couldn't seek support. Look at the hundreds of articles about plasticizers, and the Humo article, and "experts" not privy to the lab reports condemning him as a blood doper.
Why on Earth would he want to come back to that - to be described as "the disgraced" for the rest of his life? He doesn't need the money. He doesn't seem to be into fame and self-promotion. After losing two years in his prime, what race would make him want to come back? His legacy would already be ruined.
Other guys came back because they had unfinished business, or needed the money, or the acclaim. After all the trash that was repeated against him for a couple of months, with cycling media pretty much trying to push him out the door, why would he beg those people to let him come back as a second class citizen a couple of years down the road?
Basically, if you bash him, don't expect him to come back so you can bash him some more. He doesn't owe you anything.