Exactly. If you want to get into software development don't bother with more IT training. You're a sysadmin and you have some coding experience; technically oriented education won't teach you much that you can't pick up on your own. I'm not sure a certificate or degree in CIS will do much for your chances of getting hired in development either. If you think more education is important, look at pure CS programs. Otherwise, teach yourself the principles of computational theory and good software design. A broad understanding of standard algorithms, data structures, and software design methodology will serve you much better in development than IT training.

Many people don't realize that a bachelor's in CS is more of a liberal arts degree than an engineering one (well, applied mathematics). All that bullshit about "lifelong learning" you probably heard when getting your BA (mine's in polisci) is pretty applicable to CS. I've recently graduated with a BSCS and I know quite a bit of computational theory and design methodology but very little about the technical details. I don't know much SQL, I've never worked with an Oracle database, I'm not especially well-versed with XML, etc. The hot new tech with a nifty little acronym probably isn't in my portfolio. In the current job market, where no one wants to train you, this is a bit of a problem. You have some hands on experience in system administration. With some pure CS training, you may not find it all that difficult to move into a development position, even if your theoretical background is self-taught.

That said, I wouldn't leave paying job at the moment to find out.