Interesting thread and good points.
Well SinglePlayer game obviously will need bots so no worry here.
As for the Multiplayer part, I think Kadat and and biohazerd87 in particular have good points. Bots can be used as sort of sparring partners.
I think 2 points tend to be overlooked by bot programmers, and they could help keep bots alive:
1. Bots as specialized sparring partners
This idea hasn't really been completly exploited on the bot programmer side, since most bot coders focus on making complete bots players for offline play. Instead one could code bots specialized in simple training tasks.
For instance in CS you could have a bot that just behave like a moving target to train your sniping skills. You could program various movement patterns (moving in parallel, random movement, rushing on the sniper, zig-zag etc...) and the player could make snipe training sessions on those pattern. You could make some mini-game with that, so its not just some annoying shooting session. For instance on the first level the objective is just to shoot down the bot in less than 10 seconds, then you have to use a maximum of 2 shots etc...
Sort of specialized tutorials. With bot slaves
I don't think learned tactics would be revelant since human players behave differently and in different ways, but you could certainly improve your skills.
Programming such things would also be usefull for the bot developper, since those primitives behaviors could be re-used in someway in a real game.
I'm considering making such training mini-bots for IOS (International Online Soccer). I'm planning to do a set of one-on-one bots : one that do only defence on you, another that play with you and do crosses for you etc...
2. Bots vs Bots matches
Well there are computer chess vs computer chess matches, and various other AI/bots competitions (car drivers, ai soccer bot etc...).
That could be funny to make teams of bot compete in your favourite mod.
That one is only interesting for the programmers of course.
As an example again, I'm doing a system for IOS that allow you to do just this. Since I'm trying to make a team of bots for IOS I thought it would be cool to allow other bot developpers to make their own team without too much pain and pit them against each other
Its easy for IOS because there's a very simple environement (a pitch, players and a ball) so you can make a simple bot api. Would be much hard to do in a standard fps mod I guess, unless you standardize stuff (maps...)