Glad to see someone getting interested in BlazBlue thanks to EVO! I hope this happens a lot! Welcome. Here are some answers to your questions:
#1: The latest game for purchase for home consoles is BlazBlue: Continuum Shift, which can be gotten for very reasonable prices (See the link). There is a free balance patch that updates the characters to the same state as “BlazBlue: Continuum Shift 2” for the arcade/handhelds, and generally does a remarkable job of balancing the game.
#2: I can’t speak for PSN, but the scene on XBL is quite lively, and I generally find the netplay to be pretty good unless you’re dealing with someone who insists on joining 0-bar matches or something.
#3: If you don’t want to play as the DLC characters, you don’t have to buy them. By updating your game to the latest version, you get the ability to play AGAINST them online for free, so if you find yourself thinking “Dang, I gotta get me some Magical Squirrel Butler” then you can pick up whichever ones you want (All three are excellent characters.) but if you don’t feel an urge to play as them, then you don’t need to spend anything. As an additional note, Mu-12 is only available if you either beat Story Mode, or shell out about 50 cents to buy the unlock instead.
#4: There are not any new BlazBlue games in the forseeable future. There’s a PS Vita release coming sometime, but that’s just going to be BBCS2 again with a little bit of bonus content, so there’s really no reason not to pick up BBCS now.
The game is a ton of fun, but it’s very different from and significantly more complex than Street Fighter - even setting aside all the unique character mechanics (And EVERYONE has those), simply from a system perspective, there’s a LOT to know. Where SF4 has EX/Super/Ultra and Focus attacks/FADC, BlazBlue has Distortion Drives (equivalent of Supers), Astral Heats (Kinda vaguely like Ultras), Rapid Cancels, Instant Blocking, Barrier Blocking, Break Bursts(Two kinds!), Counter Assaults, Airblocking, Air Dashes, Double jumps, super jumps for everyone, a significantly more complicated throw system, and probably some stuff I forgot (Clashing!). It’s a lot of information to absorb, but the game has an excellent tutorial to present it for you. Though you may have to go through it a couple of times.
Just don’t let it intimidate you. Relax and enjoy it.