I once answered this question (obviously at the time less knowledgeable of the great game) with "his average definitely would have dropped" because the sheer thought that all the greats that I have witnessed in my time have never been able to average more than 60 (Lara, Sachin, S Waugh, Border Dravid, Kallis, Ponting, Inzy, Gilchrist etc etc.) made me believe at the time that whilst Bradman was undoubtedly a better batsman then all of them, how could he be (theoretically in terms of average) almost twice the player of the best I've ever seen?
But when you look (as Brumby said himself) at his nearest contemporaries (before and after he debuted) and what the best of them averaged (Hobbs, Hutton, Headley lucky to break the 60 barrier at the end of their career), it all turns to the one simple point. Bradman was simply that much better than everyone else. And there is no reason why, if the question is posed right whereby he wasn't just transported from his era to ours, but he started in this era with all the opportunities available to all batsman, that he'd be just as good as he was.
Its not that inconceveiable that if Hayden can have an average almost 55 and score 1000 runs every year for the past 5 years (This is no rag on Hayden as I feel he sometimes gets too much criticism on this board, but he is miles away from an all-time great and is lightyears away from Headley, Hobbs, Hammond etc. let alone Bradman) that Bradman could average 99.94, and possibly even more.
Logically, yes his weaknesses could be found out with technology, but that hasn't exactly stopped current players from not scoring prolifically has it? Hayden, Sehwag, Gilchrist and Ponting are all far from picture perfect players and do have obvious technical flaws or deficiencies. They haven't necessarily been ironed out, but they've played around it. Bradman would logically be able to do that, and most likely iron them out. Natural talent and individual ability IMO outweighs what can be coached anyway. Bradman obviously had talent that no other cricketer had.