Are there any current high end dipole speakers (dynamic)?

Another vote for Spatial.

     I have owned B&W for over 40 year, since selling my, Quad receiver, then Phase Linear powered stacked Advent grad school party system. During this meantime, I had electrostatics for 25 years, and Maggies for a few years. We also had Quads powered by Bedini. which were truly great when used from 4 feet away. In our home, we auditioned Time Windows and Dahlquist, along with Time windows.  If you want to blur the sound all over the walls, I have a near-perfect set of Bose 701's Serie II someone gave me. They have not been hooked up in my house, but they were very interesting on acoustic piano, when powered by his Bryston Electronics, which he also gave me.  
     The Bryston stuff is very good, nearly equal to my Audire equipment. I am still amazed he used it with Bose, but it worked for him. 

Listened to the M1s when they were new and was very impressed. I would have gone for Apogees at the time (just missed a pair of Scintillas which are a bear to drive but sounded very good).

The M3si is a very special speaker and your going to have a hard time finding a suitable replacement I'm sorry to say.  I wish I had a suggestion, but I'm on the hunt myself.  Another issue is cost, your going to have to spend some serious money to find something in 2020 that's full range and has the same HUGE soundstage.  Personally, I'd keep them or if your on the East Coast, sell them to me. :)

I was at the XFI Premium show in Veldhoven, Holland end of last month and can recommend Spatial and Pureaudioproject. Lots of good sounding rooms but these two appealed to me most. Open, spacious and natural. The bass does not slam but what it does do is provide great insight into the lower registers.

OB bass is sometimes a little lightweight but never boomy. Also the figure-8 radiation pattern is, in most rooms, an advantage. Without the booming the entire frequency range is clear and informative. I am using home built OB and will not bother with box types.

If more bass is needed then I very strongly recommend OB servo subs and I will be building some to augment my set-up.

douglas_schroeder's wind analogy was just 'shootin' the breeze'  :) What happens behind the speakers matters. Everything matters.

Whilst in the PAP room I chatted to ZEV the designer who is from Israel. A nice gentleman who will supply parts to the DIYer. The pair I listened to used used a Voxativ driver for midrange. There is a model that uses a horn but were not available to audition. Out on demo I think he said. He has a model using 4X15" drivers, 2 up and 2 down D'appolito fashion for those with huge rooms or need more bass.

The Spatials also really great with all the charms of OB