I’ll try.
Plugins don’t. Applications will. Everything you could do with a plugin, you always could with an application because both used hooks; it was powerful and you could do basically everything. Hooks are removed in V5. It won’t be possible anymore and it’s been replaced by a hook-points system (a.k.a. Listeners) and a UIExtension, which we don’t know as they didn’t blog about it yet. It will be more limited/restricted, no doubt. Matt said, you can do a lot, but you can’t do everything you could before. The doubt now is how much limited it is compared to hooks.
Translating to marketplace resources: my guess is that a few (compared to the totality) applications/plugins will be fully upgraded to V5. Some will be upgraded but will lost some functionalities (due to hooks it may have today) but vast majority don’t, at least in first moment; improvements will be necessary along the way.
I guess we’ll have to wait and see. Get your popcorn and have a seat. Only time will tell.
Marketplace rules will change for V5. 3rd-party devs probably will be allowed to create similar resources.