According to Entertainment Weekly, Marvel has been quietly developing a spin-off series.
"We’re told a spinoff is being developed by SHIELD executive producer Jeffrey Bell (Angel, The X-Files) and SHIELD writer Paul Zbyszewski (Lost, Hawaii Five-0)."
EW doesn't have any details for the spin-off, or they know and have been told not to reveal any of it because it would spoil the end of AGENTS OF SHIELD Season 2.
"We don’t know is which characters from the current series will be moving over to the proposed spinoff – so let the speculation being on that. There won’t be an implanted pilot episode this season directly setting up the spinoff, either (like how CW launched The Flash out of Arrow). However, story elements that are still to come on SHIELD this year will be used to lay the groundwork for the potential new series. So by the end of the season – assuming the details for this project haven’t already leaked, which is rather unlikely – the spinoff concept should be clear."
AGENTS OF SHIELD generally has good reviews after a very slow start to Season 1, but the fact of the matter is that this is a weekly hour-long advertisement by Disney for their Marvel Cinematic Universe. It makes sense to expand it as long as there's an above average size viewing audience, which AGENTS OF SHIELD does have.
Unfortunately, there is still no word on if AGENT CARTER will get renewed for another season and EW also reports that there's only a 60-percent chance of its renewal.