Nobody gets 46's in the Navy anymore. We finished the phase out about 5 months ago. Roughly 60% of Naval Aviation is Helo's, so if you want to be a helo pilot the odds are good. I don't know of any Navy SNA's who wanted to be a helo pilot who did not get it. I do know of some Marines who wanted to them and got forced to fly jets.
If you are not in the Navy yet, the chances of you ever flying something other than a variant of the Seahawk are pretty slim. We are moving toward an all 60 Navy, and the move is fast. Right now, 53's are the only other option and they only get about one or two guys a month.
If you dig around on this thread a little, there is a lot of good information on the options and missions for helo pilots (HS, HSL & HC). Advancement in the helo community is extremely competitive right now. Retention is extremely high right now, and if you want to screen for department head and command, you had better have your stuff together. There is no such thing as a "terminal O-4" right now either. If you are a LTCDR with 14-16 years in and you don't screen for command it is very possible that you are going to be told to pack your bags. Do not pass go, do not collect full retirement. Who knows what things will be like in 8 years, but that is the nature of the beast right now.