Cobie Smulders is in the midst of negotiations that could see her return as Agent Maria Hill opposite her Avengers co-star Clark Gregg in Josh Whedon’s S.H.I.E.L.D. TV series (see "Whedon, Marvel Prep 'S.H.I.E.L.D.' TV Series").  The extent of Smulders’ appearances on the S.H.I.E.L.D. series is not known, but apparently her current TV employment as the sexy Canadian anchorperson Robin Scherbatsky on How I Met Your Mother won’t present any sort of problem that would impede her participation in the S.H.I.E.L.D. series.
Smulders told the Iamrogue Website that her commitment to How I Met Your Mother "doesn’t affect" her possible participation in the S.H.I.E.L.D. series, though she was reluctant to talk about her role in the S.H.I.E.L.D. series, though she admitted that "there are definite talks going on."
Smulders is set to return as Maria Hill in Captain America: Winter Soldier, which starts filming in March under the direction of the Russo brothers.  Smulders will join Captain America: The First Avenger vets Chris Evans, Sam Jackson, Scarlett Johansson, and Sebastian Stan in Winter Soldier.  Smulders has seen only parts of the Winter Soldier script, "Yeah I have seen parts of it, but I don’t know much.  This is Marvel.  They don’t let you know anything.  It’s a very watermarked script, heavily watermarked," Smulders said referring to the tracking method (watermarking) that Marvel Studios has used very effectively to keep scripts from leaking to the Internet.