Fib - Epic mentioned games they will have some sorts of achievements and social stuff like that on their store. Most likely Construct will have to make a plugin to communicate Epic store's API. Stuff like that is usually undertaken well beforehand. And since Ashley didn't answer in this topic I guess that he is well aware of Epic store and needs no additional notifications.
Volbyte > much better revenue share for indies and less crowded marketplace than Steam
Many indies i talked to are skeptic for the moment. Bigger share and less competition means nothing if there will be no players interested in indie games. For example, in theory i can create my own web store for my indie game. I will have 100% revenue and zero competition, but no one will visit that site and those who do will (most likely) refrain from buying.
Anyways only time will tell if Epics succeed. There are others who try or tried to compete Steam (Itch io, Gamejolt, GoG, kartridge, Discord etc) and it's only starting to give effect (i mean Steam started to do smth with their outdated software and standpoint).