The successor to BRP Mecha is Dynamic D100.
Of course, we could make a new supplement about the real robot genre (Gundam, Macross, etc) but since it would require a good deal of adaptation, it would be almost surely a Revolution D100 book. The original BRP Mecha contained a lot of BRP variants that were later ported to RD100.
As a rule of thumb, products that were published as BRP originally, without big rule variants, will be ported to BRP UGE. The others are more likely to become Revolution D100 games.
Theoretically, we could do also Merrie England Age of Chivalry for BRP again, so having this setting available for both systems.