Cloud saves will be coming around February.
Achievements will be there by the end of 2019. Reviews will also come eventually – I don’t recall a date being given at any point. As stated before,
there will not be per-game forums, and Galyonkin also added that
there wouldn’t be guides like on Steam.
Developer pages on the store will also be implemented at a later date. Social features will be introduced, but it'll be somewhat different from Steam's, and he couldn't give details yet.
Limiting download speeds will also be an option. User profiles are planned for the beginning of "next year,” but I'm unsure whether he meant early 2019 or 2020.
The equivalent of Steam cards isn’t planned. Galyonkin says that they have an undesirable effect on purchasing decisions in the sense that people buy games that they don't really want just for the cards. Unlocking (in-game) items like skins and things like that will be possible but not necessarily tradeable.
You’ll be able to launch non-Epic games through the launcher, like on Steam. You can already pull in friends lists from Steam, Galyonkin said. However, importing games directly from other platforms – like on GOG -- will not be done. He doesn't see the advantage of it.
As for mod support, Epic wants to apply their Support-A-Creator program to mods as well. They don’t know yet how it’ll work exactly. What is clear is that they don’t want to sell mods but would like mod creators to somehow get some amount of money. A mod manager was discussed briefly, but nothing concrete was said.
More social media integration is being looked at. Currently, it’s already possible to connect Facebook, VK, Steam, Twitch, PS, Switch, Xbox, and Google accounts.