Given how busy things are currrently at ACN, with all time high utilisation rates and attriction rates back to 30%, I don't like your chances. Its more than likely that a project has already earmarked you out for a role. Indeed, the role which you were eventually offered may have been created from a project need. ACN need people know, not next year. Who knows what the market may be like this time next year. There may not be a need for you by then. I'd expect them to say work out your current notice, give you maybe a week or two and then thats it. If you ask a year, they'll say thanks but no thanks and withdraw offer.