Yes, I agree that the site should be merged into stats.SE, but no, I do not think that the ML folks will be happy with that.
Frankly, when I heard about crossvalidated the first time, I hoped that it would contain more ML then it currently does. It is certainly better now, but new ML users coming to this site will still mostly see stats-related questions.
A little bit disappointed by the slow growth (of ML), I signed up for ML.SE.
But now, looking at the questions and answers in the beta, I cannot get rid of the feeling that I had earlier, that most ML appliers (but certainly not all) on stackoverflow AND ML.SE are actually programmers who get excited by ML (which includes me), but cannot considered necessarily as "experts".
So ... I think that ML should grow under the corresponding tag here on crossvalidated (and not on stackoverflow) until the critical mass is reached. Then one might consider another proposal, but not now.
HOWEVER, seeing that the active ML experts on ML.SE are fighting such a merge with tooth and nail, I am afraid they will wander off when the rebel colony is forced back into the empire (Machine Learning is a duplicate of CrossValidated). All in all, I do not understand why they think that "seeding" ML questions here on crossvalidated.com is wrong but doing so on ML.SE is right.
Beside, I think that the stats- and ML-folks should learn more from each other. E.g., a little more statistical rigor in ML-validations will not hurt ...