You should release 1-2 new maps a month or every 2 months. It doesn't matter if they're mediocre or not, you just need a separate team to work on it. Every year, or half year, you should release a well drawn out map that extends the storyline. These inclusions would greatly increase the playability of the maps, instead of them getting stale after playing the same maps 50 times over.
This is just a suggestion, not a 'DO IT, DO IT NOW!' comment.
I'm not sure if the addition of more upgrades/achievements is a good thing. On one hand it lengthens the game and makes it easier for the previous run, but on the other hand it gets extremely expensive on both purchases and upgrades and the difference in price between 1 and 2 further lengthens.
I found a bug related to my sleep button. I keep the music on mute, and sometimes the game running in background, and found that when I put my computer to sleep with the game running it will unmute the music. It's a bit irritating, but I cover the sound through headphones so it doesn't overbear the air with repetitive music. Hope you find a fix to this, and great game!
I found a bug with the music. Sometimes when I leave the game dormant, and the music on mute, it will unmute itself. I have to uncheck and recheck the mute box to fix it. Hope you read this and fix it, and that your game continues to be successful and update with new content!
Also, you should increase the lvlcap to 50 or so to make the game last longer alongside increased xp earned per match and decreased cost for weapons, and something to make the game last outside the capped level. This would, in my honest opinion, make the game much better than it is now. If you disagree don't put a gun to my face, just state what you think this should be instead.
Need to increase the amount of credits you get per match, or reduce the cost of everything instead of being overly expensive for us players. Also, we should WANT to buy Ballistic Points instead of NEEDING to just to buy a ridiculously priced weapon or quickly lvl up from 5 to 6 instead of playing 1000 matches. Some serious maintenance needs to be done before this would be considered as good as CoD (which we all know is good, just yearly released).