Hyundai and Kia will offer stop-start technology within 2 years

It's not new technology but they are getting into their own realm now offering technology that's found in more expensive brands. They are on route to doing bigger and better things. They still need to branch off and create their own "Genesis" badge to be taken seriously. Hyundai's been tainted from the get-go.

Better question: Why does it take Toyota 2 years to realize their brakes suck?

The tech is not new but the recent developments and improvements in stop-start engine tech integration have seen the emergence of two competing systems, a belt driven ISG (idle-Stop-Go) device, shaped like an alternator, which replaces both the starter and alternator, and an inline system that is mounted directly on the crankshaft between the engine and gearbox. The latter being more expensive. Both systems are said to yield between 10-15 percent more in fuel efficiency while reducing C02 emissions approximately 10 percent.

The belt driven system will most likely be what is offered by value line automotive manufacturers like Hyundai/Kia, while high line brands like BMW and Mercedes will equip theirs with the in-line system. Although Mercedes might be considering the lower cost belt driven system for their A and B class vehicles.

In either iteration the biggest benefit is the reduction in C02 levels especially in city and interstate driving where stop and go traffic is notorious for creating the most pollutants.

2 years seems a long delay to shift from Europe to N. America - it's already available on Hyundai cars this side of the pond and has been for a few months now.