I'm not sure there's a problem. The people carrying older knives like those you mentioned, the G2 workers and ATS-34 Militaries, obviously aren't in the market for a new knife, so why would they mind the rate new models come out?
The people who want to keep buying new knives are afis and collectors, and they will be around when knives come out they want. Even if something comes up in life and someone misses a year or two, there are plenty of discontinued models for sale in second hand places, like this forum and ebay. The dodo was brought up as an example, but they're regularly posted for sale. Also, most of Spyderco's knives don't appreciate a lot, so you aren't going to pay a lot more for missing it. To use the dodo again, I keep seeing them for $120 or less, which I believe is under the original msrp of $140.
It seems to me the choice is between Spyderco coming out with a lot of models such that there are so many desirable ones that one might not be able to afford them all, which seems to be your (the OP's) case, or they stick to their main lines such that there is no chance of buying some models you would otherwise buy but can't because they are never produced. IMHO, it is always a good situation when the only complaint is of too much choice.