The dev who brought us the Xposed Framework, Rovo89, last week posted a version that works with Lollipop and its ART runtime. When he said "coming soon", he wasn't kidding.
The new version is an Alpha, meaning it's not final but has been tested on Rovo89's own Nexus 5 (using CM12) and Nexus 9, so that seems promising. If you've used Xposed before, you are no doubt aware that it was designed to work on Android's Dalvik runtime, which was replaced with ART on Lollipop (and was an optional replacement on KitKat).
The page also includes a link to a Q&A, which includes some good news like that most modules should work within this new Xposed Framework because they're not tied to the runtime format, especially the ones that modify apps and not system level stuff. It also mentions that he is now accepting donations, if you really insist (after resisting them for so long) but mentions that it does not mean you can make demands. So if the only thing holding you back from upgrading your device to Lollipop was the lack of Xposed, you can now give it a try.
But remember, it's still an alpha version, so there could be bugs (some were already mentioned on the Xposed thread for Samsung devices). I'm not going to be upgrading my Nexus 5 just yet, but now that I've got my Nexus 7 running Lollipop I may try it on there, now that it's no longer my main tablet, since getting my Nexus 9. If that works out, then I'll try out the Nexus 9, and then my daily driver by April or May.
Update1: after installing the zip and then the APK on my Nexus 7, I tried a few modules, and these ones that I tried seem to be working: Scroll To Top, Root Cloak, Swype Tweaks. But the Greenify Experimental options that require Xposed do not work, or rather they're not able to be activated. The other modules seemed to work after using the app SELinux Mode Changer to change the mode to "permissive" and using Xposed's soft reboot option, although when I check the Installer menu it still says "not installed". Also tried out AppOps and that seems to be working too.
Update2: I tried installing on my Nexus 9, but this current alpha version of Xposed only works on Arm V7 devices and the Nexus 9 is a 64bit Arm V8. After some reading through the XDA thread it seems that when Rovo89 mentioned running it on his Nexus 9, it may have been through an as yet unreleased test version.
Update3: for those of who mainly wanted Xposed for its GravityBox module, good news, there's an alpha of that too. You can read about it here on Android Police.
Update4: I stumbled upon this Google Doc that someone much better than me put together, that lists which Xposed Modules do and don't work with alpha Xposed for Lollipop. Make sure to take a look because some of them are noted as causing bootloops on 5.0+.
Update5: Greenify recently released an update to make it compatible with Xposed for Lollipop. Tried it out on my Nexus 7, and after a few reboots it seems to be working.
If you do try it out, hope it works out. Enjoy!