There's like a 99% chance there will be a Meta R3, but it's entirely possible Kef will wait a couple years to do it, as they won't want to steal the thunder of a Reference refresh. The LS50 doesn't really compete with the Reference series, but the R-series does.
Honestly, I don't agree. Many people (including me) have A/B tested many times the LS50 Meta against the R3 and in the end bought the LS50. I really wanted to like the R3 and I thought they had to be "better". All possible placebos and the hype-train were in their favour (they are more expensive, bigger, 3-way vs 2-way, etc etc). I tried them in several different places with several different amps. Usually when I try different speakers I'm unsure which one I prefer but in this case the difference was clear to me, I was just unwilling to accept my thoughts at first. The Metas sound way more clear, and in comparison the R3 is almost muffled. Also, the R3 is dull and a bit unengaging. You can ever hear this in youtube comparisons:
I don't speak german but you can set the subtitles to autotranslate to english (though it isn't a perfect translation, obviously). Listening to demos on youtube isn't ideal, but it can be useful to hear the difference between different speakers. To me the R3 sound dull and veiled, and I had a similar experience when I compared them against the Metas in person. The reviewers on that video also share this opinion (though they still claim they are great speakers etc)
The most popular review on amazon is also in the same line
https://www.amazon.com/KEF-Standmound-Speakers-Gloss-Black/dp/B07MM5ZRFJ?th=1
I just write this so that people don't buy them blindly. I know some people on this forum tend to *only* look at graphs, but even Emir recently stated that, for speakers, measurements only represent 70%-80% of the "truth". In my experience, most people that say the R3 are better, just think they "have to be" better because they are 3-way and bigger (that happened to me too). Trying to convince myself into buying them, I played the bass-heavy song "Teardrop" by Massive Attack and they didn't even deliver the bass I was expecting. So, even if it was true that they have better bass, it doesn't matter because you'll need a sub with both the Metas and the R3 to take care of those low frequencies anyways.