On a podcast one year ago (yes, I kept doing some research) Ben Lipsey mentions various things including the now-released Flying Blue+ app. Flying Blue extra, he says, could take a bit after Emirates Skyward+, which has three tiers — I imagine something similar here (totally spitballing here...)

Essential / Basic

For a fee of roughly 400 euros/year, you would get extra baggage kg allowance on every booking, more miles earned, 2 lounge passes, a discount on award tickets and some other perks (Emirates does some kind of miles bonus on vacations)

Premium 600 eur / year

extra pieces of baggage, all the above and a discount on upgrades, extra lounge passes

Elite 999 eur / year

All the above, 10 lounge visits, and a 25% XP boost for all XP earned

I would enjoy this myself as an addition to the perks you already get. He also mentioned solid enhancements to Platinum and Ulti which we have seen in Ulti for sure (new lounge menus, areas, car service, etc.)