Personally I think the community is taking care of the new maps issue quite well. There are some extremely well designed maps out there, and if TWI would just make the best ones official maps released with a new patch, then the maps would be taken care of easily.
With TWI free to work on other things, maybe we could get those new perk levels, new weapons, and maybe even new specimens.
I really don't mind the idea of leveling up the perks even further. Since sharpshooter is the only one I still have to get to level 5, I find myself not even playing the other perks that often anymore. Problem is, sharpshooter is incredibly boring for me to level, so I find myself quitting the game more and more often now. Expanding the other classes more would make me play more again.
Honestly the most fun I have had in this game was leveling up the Berserker. Too bad it was the first one I leveled up to 5. I just wonder how making the characters more powerful would change the game. The specimens will just get easier and easier, however if they strengthened the monsters, or added new ones, then things could be a little too difficult for the lower leveled perks. Then again, those people DO have the choice of playing on beginner level.
If the additional levels just added cosmetic changes, I wouldn't really feel as much drive to level, since I don't really care how my guy looks THAT much, especially if I needed to add on another 5 million damage just to get a shiny badge or whatever.
Still, I think more is better, anyday.