Ideas posted here are judged by the MAJORITY of yes or no opinions..
There is a huge difference between posting your opinion and just trying to put someones idea down for the sake of it and calling them "stupid" because they haven't figured something out.
If you think that it's a bad idea because it will make the game worse then fine, but none of the negative posts here are like that. It has nothing to do with everyone agreeing either, just the attitude of some people borders on blind fanboyism.
Anyhow I think this is a relatively simple improvement for the devs to make, which will also be more user friendly to newcomers. They could simply add a Next Wave: part on the HUD that shows at the end of each round in the corner. So at the end of round 2 it shows Next Wave: 3, at the end of round 4 it shows Next Wave: Boss etc.