Well if we are fortunate enough to see Walt become a biological father then I would vote for a girl. Walt has always struck me as a man's man and that kind of guy is potentially puddy when confronted with a daughter.

I figured that It would bring up some comedy into the series if Walt had to deal with twins Especially the girl.
and Just think of how nice it would be if it was twins Sarah Might not like the idea She has to carry them. but I'm saying five on the twins.

I think that him having daughter would make him want to cling to JJ too much and put stress on his relationship with Johnny, as Johnny would become competition for JJ's attention. A split pack however might bring up other problems such as WAlt favoring his own son, and ignoring JJ. But A Daughter would get what I got from My Dad.
The "Girls make babies but Sons inherit thing." My Dad lavished his attention on My brother, while My sisters and I were ignored. Then he told My brother to kill my horse!
Big mess there!

Awwww...
A girl!