Most "mainstream" conflicts have been covered quite well by now. Most collectors have been in the hobby for decades so their WW2, Napoleonic and Roman armies are already sizeable.
I guess what catches attention nowadays is
a) "mainstream" sets that are vastly superior to existing ones (say: Emhar WW1 U. S.),
b) supplementary sets for "mainstream" conflicts (say: Strelets DAK mortar set),
c) niche units for "mainstream" conflict (say: Strelets Long Range Desert Group),
d) new ranges for huge international conflicts overseen so far (say: Strelets WSS range).
Not to start yet another wishlist but to illustrate the above, ideas could include
a) WW1 Serbians in summer uniforms,
b) WW1 French support weapons,
c) WW2 Greek,
d) Russo-Japanese War of 1904/5; Sino-Japanese War of 1937-45 (the Japanese have been covered rather well but there is just one set for the World's biggest army, the one of China)