They officially announced that DOA token be refunded.
Then is it going to be like below
No. ETH funded * (Number of DAO holding / Total DAO)
Any idea on it?
Good luck with that. The Ethereum foundation would have to do a fork to implement this. The fork would basically replace the whole blockchain with an altered version. This is going to take months if they chose to do this. They also better make extra sure that the replaced DAO code and replaced ETH code has no bugs or vulnerabilities that could make the fix worse than the initial problem.
If they hard fork any DAO refund would be at ICO price, wouldn't it?
All the ETH would magically appear back in the original DAO address and every DAO token holder at the time would be able to extract their share of the ETH. No telling what ETH will be worth in BTC or fiat by then or if it will even have enough miner support to keep the network viable. Time will tell. It's going to take a monumental feat to keep the ETH scam token train running that long.