In the nicest possible way the forum is a quite conservative place with many not liking change.
The introduction of the E89 was really hated on, weight, folding roof, wheels cracking, size, handling! Most of all because there was no M variant when BMW had access to that amazing V8, 100hp on the S54, 2 more cylinders and weighed almost the same.... looked like it could have been a great combo with some M sharpness upgrades. Alas it never happened.
Its also the fact you cant buy a "new" Z4, currently the maximum any Z4 is about £30k but the vast majority of current Z4s are 5-18k. The new one is slated to be 40k but i very much doubt that as the E89 was more expensive, I could see these easily running to £55k. Were talking about huge differences in price meaning different buyers.
Its very doubtful anyone looking at the "current" Z4 options will be in the market for this, 10K E85/6 3.0SI even a 20k E89 35IS, there will be a 30-40k difference in price.
With the gap of 2 years since the E89 was last produced I would say the current owners probably arent the target market. I doubt there are many 1 owner Zs left the ones that are... is it really going to be a mass migration of Z4s coming onto the AUC market, Doubtful.
The target audience of the 55k Z4 have moved on because BMW left them with no option. At the end of the production run even with the discounts the Z4 was expensive vs pre owned they just weren't very attractive and the numbers at the end of that period were minuscule.
The people who did buy cars at the end of the run was because the majority of facelift cars were sold in 35IS spec but with very few options and were sold in small numbers so were hard to get hold of. The only way to get what you wanted was to order it new and the fact no new Z4 had been announced or was even on the horizon with the only chatter being a hybrid which excited... no one.
They will be trying to win those customers back that have moved on to another BMW or brand.
Its also a big risk buying these things, the E89 had awful residuals, to the point when the facelift came out they put huge discounts on 35IS models with no spec to get Z4 owners to upgrade because the boxster was the same price but a far better drivers car and the E89 was slated by the press. The residuals have been so much better on the Porsche alternatives. A fully loaded lowish mile E89 35is wont set you back much more than 22-25k yet a similar 981 box/cay will cost you 32-35k for a standardish S all the way up to 55k for a GTS.
You also have to factor in the financial situation between 2009-2014 it wasnt a particularly stable time so that was also a factor. 987.2 Boxster and Caymans sold in very low numbers too in that time but were available from the end of 2009 to early 2012 (18 months) before the 981 was introduced.
The E89 has gathered traction in the used market because it wasn't received well and they are cheap just like the Z4MC was, they have become real bargains with lots of performance on tap, with comfort and they are good looking cars. With low end 35I being 13k they are absolute bargains what ever way you look at it. Makes them available to lots of people that wouldn't have bought one new. I bought my 4yo Z4Mc with 45k for 17.5k in 2011, because i couldn't afford the insurance on an E46 M3.
Forums are full of enthusiasts and unfortunately BMW doesn't cater for these people anymore, even if they make an M version it will be on the same line as the M4 style cars. They are quick and purposeful easily being weekend and dailies. The old M cars with notchy gear boxes and poor fuel economy wernt that suitable as dailies. You could use them as dailies but you had to really love them... aka an enthusiast.
Now anyone can drive the newer gen cars quick, there is no effort plant your foot and go.
The main issue is all of the modern M cars have lost the essence of what an M car is, the M brand is so diluted that almost every model has an M variant and sub M variant like the M140s etc. BMW are in it to sell cars and have made this perfectly clear. They are not for the enthusiast. Look at the M140 they have sold a shed tonne, those numbers are a success and BMW will be happy to make more of these mid way cars.
At the end of the day people that buy cars are the mass market, they dont want spine shattering ride quality, only suitable for a weekend a&b road blasts. They want comfortable cars, with the best tech, quick in a straight line because most will sit on the motorway and they want to look good while doing so. An extension of their own persona.
BMW obviously feel they cant compete with the box/cay market with the Z4 which is why the E89 was produced. Maybe BMW feel the M2 and M4 are more suitable as competitors... although again I wouldn't call either a sports car but a fast saloons. This generation Z4 looks not to be a GT and not an all out sport car but something in between that can tickle your fancy in both areas, while maintaining a 6 cyl motor and 2 seats in a world where 1.8 and 2.0 turbos are the new generation. Im not really sure what that is, but it is what it is good at many things, master of none.
At least they kept it a 6 cyl, although a turbo it sounds very purposeful. Its very hard to get excited about smaller engine, worce sounding cars. I cant get excited about the Alpine although interesting it just doesn't do it for me, the new box/cay again amazing car but there is no emotional attachment. Its not just BMW its across the whole board. All the options for me are lacking and cars that generally are exciting are in 7-100k mark which will never be affordable to me.
Even at 55k the new Z4 will have to compete with AUC pre owned cars that are 2-3 years old and maybe were 20-30k more. To many they may be more appealing like a 911, F type V8S for example. Most of these cars get 2 year AUC warranties and are also current.
Its very easy to say this is what it should be, but BMW wont make a car specific for your needs. The difference between what you say you want and what makes you part with your money are two different things.
Often the opinion of a small group vs a years of market research and analysis are polar opposites.