Dude, it's so funny you ask that since I JUST finished writing a blog on that exact topic!
I believe that if you want to optimally improve a type of muscle action you need to train it. Eccentric, isometric and concentric actions all use different motor patterns and it is quite possible to get strong in one and not in others. Furthermore I believe that eccentric and isometric strength are important in lifting strength for many reasons.
I see eccentric strength as "strength potential"... the higher your eccentric strength is versus your concentric strength, the greater is your potential for lifting improvement
Having a high level of eccentric and isometric strength make full lifts "easier" by making the lowering an transition phases easier. For example if you are super strong eccentrically lowering a maximal squat will be much easier than for someone with equal concentric, but less eccentric strength. So you expend less energy during the eccentric phase which leaves more in the tank for the lifting portion.
Insufficient eccentric/isometric strength makes it much more likely that you will lose proper position during the execution of the lift, which makes your technique less stable.
And there are other benefits... is it the next big thing? No. But emphasizing eccentric and isometric development can play a role in the development of strength especially in those for whom these types of strength are lacking.