I think Tosh could have been more interesting, she had moments where you could see the potential but the writers had assigned her to the "single, lonely geek" role I guess. And her pining for Owen was pathetic most of the time, not dramatic. They could have taken her character in a much more dynamic direction after some of the character development in the first season.. unfortunately aside from Gwen and Jack, Owen had the most character development. Ianto is getting there but he's actually turning out to be a somewhat pathetic guy now as well.
I don't know if I'll continue watching next series or not if they make these proposed changes, though I wouldn't mind seeing Cap'n John step in for a series if say Jack disappeared again.. I also wouldn't mind more info on the Time Agency playing into it, but I'd guess that is mostly Doctor Who's baliwick.
I'm waiting and watching.. it would be too bad if Torchwood were ruined by its own success.. I mean the change from BBC3 to BBC2 was supposed to mean it was "getting promoted", it'd be a shame to have it become too formulaic or dumbed down. Overall series 2 was far better I thought because they focused on the team and cut back on some of the needless "sexy" elements where they didn't fit. First series was trying too hard to be about "adult" themes at times that they didn't always include it to enhance the storytelling.