Ok so Overlord (a developer from WarGaming) has released a partial list of things to come in 7.4, he does say that there will be more closer to release, a release date has not been said but hey 7.3 has just come out. Here's the changes/additions straight from Overlord's Blog:

Let me just add, NEW GAME MODES, FINALLY

1. 
   Extension of French tech tree
   • SPGs:
     • Renault BS
     • Lorraine 39 L AM
     • AMX 105 AM
     • AMX-13 F3 AM
     • Lorraine 155 (50)
     • Lorraine 155 (51)
     • Bat. Chatillon 155 (features cassette reloading or autoloader)
   • TDs:
     • Renault FT AC
     • Renault UE 57
     • Somua Sau 40
     • S 35 CA
     • ARL V 39
     • AMX AC de 100
     • AMX AC de 120
     • AMX 50 Foch
   • MT:
     • Renault G1R
2. New premium vehicles previously available only to supertesters:
   • Soviet premium heavy tank of tier 8 Object 252/IS-6
   • German TD of tier 8 JagdTiger mit 8.8cm KwK 43 L/71
3. Two new maps:
   • Wide Park. This map is based on Munich landscape and contains a large city part.
   • Airport/Airfield. The map features airport located in the desert.

• multiple UI improvements, especially the design of tank trees
• new camo patterns
• new game modes - Assault and Counter battles, both entered the final production stage
• new sound effects
• improvements to the current team damage reimbursement mechanics