MOTM/5U is not dead by my account.
All my modulars (except the original digisound and Aries modular) har been worked into 5U format with 1/4" jacks. I have several modular cabinets in various formats (dot.com, custom wooden, rack etc.) with MOTM/5U format modules. Lots of synthesizers.com modules and moog 5U format modules, as well as many MOTM-format modules (mostly Oakley modules and DIY now). I perform live (mostly Berlin school sequencer stuff) and haul modular cabinets to gigs (just had the 15 years anniversary concert with my band), and the large modulars are essential.
Also; in the studio, I really like the big format. Suits my working style and fingers much more than those small things.
That said; I am not oblivious to the fact that large format modulars have fallen off in comparison to Eurorack format modules. I have run the Norwegian analog synth gathering for 10 years now, so I do notice the massive increase in Eurorack/Fracrack format, but I also notice this: a lot of people getting small format modulars tends to either
a) not have a clue as to what they are doing, and so...
b) sell off a lot of their stuff
c) mostly make unstructured blipp-blopp music
While in comparison most MOTM/5U users
a) really know their analog synths and how to patch up sounds
b) rarely sell their stuff
c) make (more or less) stuctural and/or tonal music
This is of course an oversimplification, as I have met Eurorack people with great music and huge knowledge, but what I said is really is a general tendicy.
I think the reason we (?) or most people think MOTM/5U is dead is this:
1) Some of the key players are less active now. Paul Schreiber used to be ∗very∗ active on mail lists and forums. He is still there, but a bit more subdued. So we are not sounding off all that much.
2) There is still a lot of MOTM/5U modules (I bought a few last year, and was amazed at how many new manufacturers there were - even some mostly Euro-rack manufacturers have started making MOTM/5U size modules) - but (and here I go): this increase on MOTM/5U is completely drowned out by the massive amount of new Eurorack modules flooing the marked!
3) And not to forget self-fullfilling prophesies: Everybody is saying 5U is dead, so it must be true.
But, yes; I have lived through many "format wars", and never in my life thought LP (that is vinyl for you youngsters) and cassetts would return, so who knows?