Just so I've covered it, I'll be looking at updating to 1.14 too. Hopefully I'll be able to jump straight from 1.12 to 1.14, providing everything works well, but I may need to run it through 1.13 for a day or two to covert the world over. I'll see how it goes...
Updating the server is my main priority though for next week. No promises, but my plan is to get as much working as I can by then.
Monday Update:
I tried running the latest versions of all our plugins in 1.14. 6 of them flat-out refuse to load, and 10 others have errors, some quite a lot. Those 16 contain some of the major plugins we use though, meaning I'll definitely have to get them working before I update. Aside from that, 5 of the plugins have already got a 1.14 version compatible available, which is a very quick turnaround. 51% of the plugins we use have a 1.13 version available too, and many of the others I'm expecting to work relatively well. There's a chart somewhere at the top of this thread which shows all that data in real-time as I test/update stuff. The world converts okay, from my tests, although the VC world is >100GB, while I've not decided how to update yet. I could do it all at once, which could take hours/days, or I could have chunks update on-the-fly as people go to them, which could work, but would induce lag when chunks are being loaded for the first time. On the topic of lag though, 1.14 is awful. I don't know how it passed through quality control at Mojang, but the server runs incredibly poorly. Dinnerbone has claimed they're releasing a 1.14.1 though "soon" which should fix much of the lag. Until that comes out though, 1.14.0 is definitely not in a useable state on servers.
In terms of the other content I was working on last year, I was hoping to get it ready for 1.14 as it brought a bunch of cool back-end changes that would make my "hacky" features a little less buggy, but the update dropped earlier than I expected it to. I'll try and work on them after my exams, and get a bunch of new custom content added to the server at some point. There's something else I've been working on for literally 5 years which, last time I checked, worked quite well, which I hope to implement soon. One major thing I'm waiting on for that is a bug Mojang need to fix, which I reported over 2 years ago, and just last month Dinnerbone categorised it, so that'll probably be a while coming.
TL;DR: 1.14 update is okay. Very laggy, some plugins broken and some I'll have to re-code. Some other plugins work okay. Waiting on 1.14.1 for a smooth update. Other custom content will be worked on over summer, but I'm not setting a final date for that