if you're talking about a board strictly for park, you can't go wrong with any of those 3.
if you're into the bigger jumps I would go with the stairmaster. I got to try all 3 of those boards this season and I found that I had the most fun in and out of the park on the k2 www(out of those 3)
I absolutely recommend looking into the Capita Horrorscope too.
I want a sintered base too so next year I'm going for Evo-R also because they softened it up a tad at the nose and tail. I'm hoping that Capita comes out with the Stairmaster Extreme with FK because I love my Horrorscope but its extruded base is not so great.
And for the answers to your questions:
i don't think there will be any change in next year's WWW rocker.
TBT is great but the only thing stopping me from buying a Bataleon is their board selection. They do not have a board that has the flex between the riot and airobic and a sintered base. Extruded bases really take a lot of damage so they'll last like 2 seasons max.
Wouldn't 152-153 be too small? I'm 5'8" 140 lbs and i ride a 155 for park.
fuck no, im 170 and i ride a 152 park and i couldnt go bigger and i dont think im alone on this. if you want a pure park board at 140lbs you are easily looking at 148.
and to someones comment about a stairmaster fk, as of right now there is nothing known to the public about it. i would not say it is impossible on the extreme level(not basic stairmaster) because the indoor survival is basically the same board as the extreme with different preferences.