We already have the PaK 36, PaK 38 (with conversion), and PaK 40 as well as the 88, so for German WW2, that covers pretty much everything the typical table top-gamer would need to play games like Bolt Action, Chain of Command. Operation Squad, and so on.
BTW, the PaK 36, 38, and 40
are fantastic plastic model kits (5-Star). The crews could be a little bit better though (3-star). The 88 looks like another fantastic plastic model kt, but I have not actually assembled mine yet. But I'm sure it will be 5-Stars.
For the Allies, we will get the US M2A3 75mm, the US M3 37mm, and the British QF 17/25-pdr gun.
So, what I would really like to see sooner than later are:
ZiS-3 AT gun for the Soviets
US 57mm AT-Gun M1 AT-Gun
British QF 6-Pdr AT-Gun
Note: There is great potential for the
57mm AT-Gun M1 AT-Gun and the
British QF 6-Pdr AT-Gun plastic kit because the same sprue for the AT-Gun can be setup with the needed bits and parts to build either the American or British gun (Standard or maybe even Airborne versions). As for crew, separate American and British crew sprues can be added. Pretty much like what Rubicon Models did with their Jeep kits - same Jeep parts and bits but different US and British driver/passengers.