-Quint and Slur are not able to be obtained currently -Trill is able to be fought against, but only in the Development Beta -Tomahawk, Galaxy and Freeze Man can be fought in Starforce missions, but due to a bug, Strike Man does not
And for your last point, I get the fact that you're kinda confused about where the next update is, I really do. But the staff just hasn't randomly called it quits, though, most of us have been working on the latest update for a while now. The thing is that sometimes we have other responsibilities, and our own head developer himself had to take a break for a while, due to other responsibilities. Rest assured, Prototype isn't dead, and I don't want to make any promises, but I know that we'll get the Update out someday. There's still plenty to work on though, and the massive amount of changes that'll come along with it might make the wait worthwhile!