Forget about 'all big miners', what if Jihan Wu and maybe just one other guy set out to do this? They'd probably be successful.
They would be succesful and in fact there was a moment in early BTC history when they had over 51% of BTC hashpower in hands of one farm but its counterproductive to attack assets that your business relays on.
Computing power rises quickly, there are possibilities to do it. BTC is not bulletproof. Although its not worth to target it and make fuss about it. Because it will loose value as soon as people will find out that there is someone who can rewrite wallet balances.