From what I've been explained, LC is being migrated into AEM Forms, which is a separate module of AEM. The only parts that are not (for now) are Process Manager and DRM from my understanding. The Adobe topology  shows that forms processing is done on a Process server which is an Author. For Process Manager, then you use the ES4 component of AEM Forms.
So are you suggesting that we still use ES4 for all forms processing and bypass the AEM Forms Process server? I agree with Darren in that AEM Forms is lacking in its ease of implementation of forms processing in comparison to using ES4 directly.
I do not think its accurate to think of AEM as a replacement to LC. They both perform different tasks. AEM is about web management and building world class ditigal marketing experiences while LC is a powerful enterprise tool for document services. You can use both together to perform many useful tasks. Now with respect for watched folders in AEM, you can easily write custom services that use JCR events. For example, if an asset is dropped into a jcr folder, you can write a service to respond. We have a community article around jcr events and osgi. See http://helpx.adobe.com/experience-manager/using/events.html.