HybridHBNot with this Massdrop version of the O2, if you choose the desktop option it will come with the larger 1/4" headphone jack.
JDS Labs can do a desktop version with a 3.5mm jack but it would cost $147 + shipping.
HybridHBI think you're mistaking in and out; if it's so, what's wrong with sticking a 3.5 to 6.35 adaptor in a 6.35 socket? It's definitely more painless than the opposite (6.35 to 3.5).