This has been on my mind a bit lately.
I’ve always been a proponent of whatever wheel size I’m currently riding, and down played all others. Aside from a brief stint with a 26, I’ve tended to stick with bigger wheels. Currently a 26+ and 36 are my Muni’s.
Anyway, kind of thinking about a 24" now for freeride type stuff…
I hope not! I have three 24" muni’s in my garage. I am hoping for a few more 24" fat tires to go on my latest muni. With that said I can’t stop riding my Oregon.
It may be a fading size, but I think it will be around for a while. There was certainly some hot 24" MUni riding at the 2014 California Mountain Unicycle Weekend (last weekend). Amazing riding on some very challenging trails!
My “best” Muni is still a 24" (Wilder, which I received in 2003). However I expect my next one will be a 26" KH.
No… because a 26 does not easily fit in my suitcase
That’s clearly noticeable when you’re looking for a new MUni tyre:(
That is true that the choice of tires reduced over the years and the unit price of the remaining tires still produced is slightly higher than for other sizes.
However… it seems to start again being trendy thanks to the fat bike movement. And based on the trend we saw with the 26in, after the fat tires comes the mid-fat tires (3.0). So, 24in is coming back in the game for the pleasure of muni riders 
I’m finding my non-fat 26" to be obsolete and my 29" muni to be too tall for anything technical (and too scary during UPDs). I’m in the process of building a 24" simply because it is more lightweight, slightly less tall, and gives me another option for something that my fat 26" probably wouldn’t do well on. I think knobby 24" tires might become “dead” in the biking world, but I imagine it will still hold signifance in the unicycling community. That’s my lowly opinion, anyway.
I use my 24 for anything technical and my 29 for non technical… Cant really see the point of having a 26 because its not a big enough difference.
So for me the 24 is alive and kicking 
I’m a fairly small guy so riding a 26 on technical terrain would be like a normal sized person riding a 29 in technical areas… I think it’s like the small persons(’?)s 26".
If my KH 24 is dead, then it’s the most awesome ZOMBIE MUni there is! In fact, we should makes a series with only 24er MUnis called “The Rolling Dead” 
I wouldnt mind to own a 24" and find the difference in the two
…on second thought, i have already 5 in 7 months,
…wife would mind.
There’s nothing like assaulting some hard-core trail with a 24x3. If all you ride is 26 or bigger, you are really missing out. I often look back over the trail that I ride through and think to myself, “how the h***” did I clean that???"
Do it! 
On their website Chainreactioncycles has 14 different 24" MTB tyres. For 26" the number is 273.
Maybe 24 is a dead size for bicycles, and therefore the 24 muni will die too. I hope not.
As long as there will be pre-teen MTB clubs, there will be the need for some MTB gears in 24".
So there should be a stabilization to a low number but still existing.
The hope is to see the size get back some love with the fat bikes wave 
Do you really need 273 tires?
Only need a couple that will work with a uni and a muni…
If none of the 14 fit my need, then, yes, I need more choices. When I was shopping, everything was offroad or square profile or high in the middle or too wide or too narrow, etc. I ended up risking it with a squarish one which thankfully ended up working out fine, contrary to the usual advice. A Cyclops would have been ideal if my frame were just a little bit wider.
you might also have noticed that only four of the 14 are wider than 2.35"
The only real negative about 24" Munis is the lack of tire selection and availability. And that’s a pretty significant negative.
I hope it’s not dying. Life without my 24" would be misurable. Some more tire choices would be nice though.