Apparently his last post on bitcointalk was in 2011 or so,
Actually December 12, 2010 (depending on your time zone).
does anyone know where he went (in terms of the Internet, is he still developing bitcoin or has he left the scene)?
Nobody even knows who he is. He disappeared and hasn't been heard from in over 4 years.
He might still be active on the internet and might even still be participating in Bitcoin without anyone knowing who he really is.
Personally, my guess is that he's dead.
I'd like to think if anyone knew who Satoshi Nakamoto was it'd be Mr. Finney:
Hal Finney would probably know who Satoshi was, or in a plot twist, maybe Mr. Finney was Satoshi all along...
We'll never know. RIP Hal Finney.