In an old discusion you said that they work on the 1.14.x (2018). But now we alredy have 2020 and the new Minecraft Version 1.16.1. What I whant to say you are the only people how made a server for forge and plugins and so many people want a server like this in 1.14.x - 1.16.x. So PLEASE make a new Version.
They are actively working on getting to 1.14.X. They are making steady progress which you can follow on the sponge-discord or github event.
They are working on it, just give them time.
Once 1.14 is up and running, getting to 1.16 will be a lot faster too.
Stay patient, they are working on this.
Remember, everyone on the Sponge team are volunteers, using thier own personal time to work on Sponge. Doing massive updates like this takes a lot of time and effort and isn’t as simple as changing a few lines of code. There seems to be a lot of difference between 1.12 and 1.14 (as you can probably tell by the fact many modders are struggling to update), but once they’ve gotten to 1.14 they’re updating much quicker, having laid the groundwork.
Please be paitent with the wonderful souls who are working on this project, they’re doing a great job!
If you want to help, they do have a Patreon that you can support