The Matchless cab is coming for sure.
I hope to see in future updates:
Basketweave 4x12 G12-M20.
Hiwatt/WEM 4x12 with Fanes.
Better Alnico Blue, modern variation.
Better 4x12 Brit v30 (Marshall G12 Vintage), the current one is terrible.
Marshall 4x12 with G12-65 from the early 80s, everything from ACDC to Metallica used these, painfully underrepresented speaker.
More Greenbacks (G12-30 75Hz, G12-30 55Hz, Modern G12-25), there are so many greenback/blackback variations throughout history including the latest Heritage series, one is not enough.
In all honesty, I can create infinite number of excellent sounds and even recreate artist sounds with what we already have by using Dual cab and carefully tuning the setting. Additional cabs will allow even more versatility with less fiddling to achieve results faster or even instantly for people who don't like advanced tweaking.
Another element is curiosity, I love to try rare vintage cabs or cabs that were famously used by artists on certain recordings.
EDIT:
I know Fractal is working on similar cab tech and I'm pretty sure this will make it very though for IR vendors to remain relevant once Fractal jumps on that bandwagon.
I also think that Fractal will do this better than Line 6 or NDSP by using more sampling points for each speaker and having several variations of the same speaker type like they do with their amp models, storage/memory space and processing power are non-issues.