Does Stacking Wireless Speakers Sound Feasible?

I really don’t know the techniques KEF uses to make this work. I assume they use a transmitter, connected to your source, that sends the left-and-right signals to the respective speakers. I don’t believe the speakers are connected in any way.

I’m not planning to build the array anytime soon (if ever), I just thought I’d throw it out there as a "thought experiment". BTW, KEF is offering wireless speakers costing much less than the LS50. If the dreaded "comb filtering" isn’t a show stopper, one could build a modest array and add to it until it satisfies your particular circumstance.

P.S. Is comb filtering an issue with sound bars? there are a ga-zillion of them out there. You'd think we would have heard about this by now. 

A sound bar isn't a simple array. Generally they are either two clusters that are providing vanilla two channel stereo, or they are presenting the multi-channel mix, just all from in front of you. Some higher priced units angle the dispersion of the surround channels to bounce them off the walls first, perhaps enhancing the surround illusion.

What they are not doing is all playing the same mono or summed signal, which would indeed create a comb filter.

Maybe not the same signal but certainly the same frequencies are emerging and interacting from up to three channels. 

Please stack a pile of LS50 wireless speakers...take a chance...I just want to see it...do it...also, what if an apartment neighbor has a pair of these things and his speakers pick up your front end and vise versa? Well? What?

One technical concern is that KEF embeds an "identity" code in the transmitted signal that keeps a stereo pair "private". Like using two identical subwoofers with remote volume adjust, there has to be a way to adjust volume one-at-a-time. Some remotes have an A/B switch to keep them separate. Like I said previously, I don't know what operating system KEF is using.
As to your stacking request, I'll gladly accept any contributions to make this happen! I suggest you send a pair of LS50s to "get the ball rolling"!