I think a new 1/72 Vulcan is odds on judging by reports of various surviving airframes being measured over the last couple of years, especially ones part stripped allowing access to early features hidden or removed by lster mods. It needs doing before another firm cashes in.
Sadly I think a Boomerang (and Wirraway) are too exotic during these lean financial times, and however much I would also like new O-1 and O-2s I can't see it happening. Also revised 1/72 Blenheims with new upper wings correcting the biggest error...unlikely but can hope.
So what about other plausible ideas?
1/72 Spitfire 24 and Seafire 47. Oddly missing as they represent the last of the direct lineage. The Spit could be modified from the 22 mould with a new lower wing, but the 47 would be all new.
1/72 Single seat Vampire, or even a NF variant. Special Hobby have the field almost to themselves atm and a new mainstream kit is needed. So many variations and colour schemes to choose from could mean many reboxes over many years.
1/72 Meteor. Surprisingly rare in the scale with most being old, hard to find, or not widely available. Special Hobby NF variants are still fairly new so I would expect either a F8 or T7 for maximum early sales.
1/72 P/F-80. Surely a no brainer especially for the US market. Throw in a T-33 at some point too and you have oodles of operators and colours. Sadly I feel the ancient mould may get a Vintage Classic release instead which would be a real lost opportunity.
1/72 Hampden. The missing early war twin. With an example being restored I doubt the designers haven't had their measuring sticks out on more than one occasion. My Crystal Ball insists on seeing a Russian Torpedo Bomber...
1/72 T-6 Texan. Another widely known, widely flown type. Could Airfix get rights to the Academy tool? Or would they go on their own? A carefully designed new mould would open up more variants than the T-6G that dominates...a proper Commonwealth Harvard perhaps?
Whatever they go for I hope for some more smaller subjects as there's been mere pickings for the shelf space limited modeller in recent years, a potty as the first half of the Hornby era garnered a fair few little uns.
I'm sure I could think of more, and I haven't even touch other scales or non-aviation subjects yet. Maybe later...