Do you think cardano will over take ethereum in terms of tech with voltaire being worked on this year. Along with erc20 converter for easy conversion to cardano via ethereum. 
No, Ethereum is ever developing, they already have a scheduled update that can bring another hype to the Ethereum market. Besides, technology can be easily copied or modified if released in public, so I do not think that ADA will overtake ETH in terms of tech for long. Besides ADA had been known for its delay so I do not think that it will take ADA a short time to develop such technology. It is more probable that ETH could have developed something much more advance and released it earlier than the current development of ADA tech.