If you're worried about wasting money, your concern can be much more profitably employed elsewhere; this whole thing costs less than the cost overruns on a few F-22's or F-35's.....
From everything I've been able to discern, this is mostly a big deal on the usual hyperventilating gun blogs and among overly excitable internet "experts". The fact that the "new" gun is a newer version of the old gun is already by far the most rational and cost-effective choice that could have been made, with minimal changes in training, materials, tools, armorer support, etc. Sigp.220.45 can correct me if I'm wrong, but it's my understanding that the FBI introduces "new" guns by simply starting to issue the new gun to the new starting classes of agents, not by collecting and scrapping everyone's current gun. So I don't have any particular anxiety about my taxes being wasted in this case.