You'd still have to convince most users and stakeholders of Bitcoin (merchants, exchanges, etc) to update to the new version in order to avoid a Blockchain fork, where both sides of the fork are likely to lose and the currency is destroyed.

As the owner of 51% hashing power, you can try to convince the network to update by holding it hostage and threatening a DOS attack by mining without verifying transactions, but I don't think that would be economical either.