Mmm, no. If the four largest mining pools go for it, but the various exchanges and online wallets do not, then you get a very dangerous fork where you now have

Mmm, no. If the four largest mining pools go for it, but the various exchanges and online wallets do not, then you get a very dangerous fork where you now have two separate currencies, and have the possibility of double spends. The nodes that are not updated to allow these larger block will keep on going along with their chain, just rejecting the other chain as invalid; and the ones that do accept the larger blocks will probably see their chain as longer and so only accept that one. That fork means that until all of the online wallets, exchanges, and anyone accepting Bitcoin directly realize that there are now two different currencies, all kinds of fun can be had with double spending.