Most of the big weapons manufacturers view change as synonymous with making money.
On the one hand H&K would be more than happy if NATO "dumped" the 9mm - they get to bid on the contract to replace the thousands and thousands of MP5s out there.
I'm all for getting the troops the best weapon systems money can buy - but this is a money waster IMO. The money would be better spent in so many ways...
Getting more quality snipers and sniper rifles out in the theater would be one suggestion.
Better armor - body armor and hardened vehicles, or give the tooops more Bradleys to drive around in vs the Hummv.
If I were in the field and I had a choice between them spending the money on new pistol trials or just finding a way to support my unit with a MK 19 or a MK 47 - I'd keep whatever old pistol I had and take the grenade cannon.