Scott posted essentially what I was going to say, so I'll just add a related observation. IrfanView, the popular image viewer for Windows, goes to some effort to make Save harder than Save As. The toolbar button with the common Save icon actually performs Save As. The toolbar does not even have a button that does the standard Save.
I presume the author designed it like this because doing Save on an image in potentially lossy format may be destructive. As is, the program makes it more likely for users to invoke Save As instead. Sometimes it is annoying, when you do want Save, but the safety-first approach has helped me on a few occasions.
Which is to say, please do not merge Save and Save As. If anything, they need to be as clearly distinct as possible to prevent costly mis-clicks.