I think some of the new stuff must be in theater, and in use.
The UA 81st brigade has at least 45 M-777s. But their ammo is limited - the orcs fire 100 shells, the UA returns 3. The rest of the M-777s are reported shelling Snake Island - a hundred or more miles away.
The new stuff is too little and too late to make much of a difference; this is a WWII and WWI style combat where arty is king. Soldiers go weeks without firing their rifles.