My wild guesses...
I think more EF-S lenses with STM (18-200mm, 15/17-200mm, 17-55mm, ...) is a safe bet. Maybe an 18-270mm f/3.5-5.6 IS STM to compete with the Tamron.
The EF 35mm f/1.4 II - it's old, and the Sigma 35mm f/1.4 is gives it a very good fight.
The TS-E lenses are waiting for an upgrade, so TS-E 45mm mkII + either TS-E 90mm mkII or 135mm (near macro?)
A new ultra wide lens, e.g. 14-24mm or 16-35mm mkIII. Note that the 16-35mm mkII was released ~6 years after the mkI, so there's a precedent for such a quick upgrade.
A 50mm upgrades, maybe 50mm f/2 IS USM + 50mm f/1.4 with proper USM.
Maybe a 20mm with better IQ to give APS-C cameras a good 35mm equivalent?