I also see the writing on the wall for all my Lightolier Compose X-10 stuff - I have dozens, and they will fail eventually. I've been testing the waters with wifi stuff - Shelly and Tasmota. So far so good - seems reliable and inexpensive. But two things are holding me back from moving forward with replacing X-10 with wifi:
1) I prefer my lighting schedules to be managed by the Elk M1G - it never fails, unlike Homeseer while does crash periodically. As far as I know, there is no way to control wifi stuff via Elk rules, and I doubt there ever will be. I'm also playing with Home Assistant which has been pretty reliable (only 1 crash in about a year), so that may be an option to run my lighting schedules.
2) I just don't see enough options available from the manufacturers of wifi stuff. I'd like to see more decora style switches and some in-wall outlets. The Shelly relay modules are still a bit too big to fit into an electrical box behind a standard light switch, especially in a multi-gang box situation. The heat given off by my Shelly modules does concern me - they seem to run much hotter than my X-10 devices.
I gave zwave a good test of several years, but I find it to be way too flakey for set and forget lighting, probably due to the Homeseer implementation. I frequently lose connectivity, I often see corrupted configuration files, interface lockups, and unexplained weirdness. I give up.
I've considered UPB, but I am reluctant to jump into a system that is almost as old as X-10. If wifi doesn't pan out, this may be my route, but it is very pricey.