Papa Vinyard here, now here's a little somethin' for ya...
While three of the key AVENGERS have gotten multiple standalone movies, including IRON MAN (topping the list with 5 appearances counting his cameo in THE INCREDIBLE HULK), CAPTAIN AMERICA, and THOR, Bruce Banner a.k.a. The Hulk hasn't taken center stage since Edward Norton's take on the character back in 2008. After the massive fan reception to his character in THE AVENGERS, including many of Marvel's own people describing him as "the star of the movie," it seemed inevitable that the character would warrant another solo go-around away from his fellow Earth's Mightiest Heroes.
Well, the original live-action Hulk may have let the cat out of the bag earlier than Marvel intended. While discussing the character during an interview for a Minnesota radio station (which was quoted by Latino Review), Lou Ferrigno dropped this choice tidbit:
"Now because he saved the day they're making another solo Hulk movie after the second Avengers comes out."
Obviously, this is Lou Ferrigno and not Kevin Feige, so it's not 100% certain he has the inside skinny on Marvel's plans for the character, but it seems believable they'd want to capitalize on the character's resurgence in popularity before digging into "weirder", more obscure properties like DOCTOR STRANGE or BLACK PANTHER. Bruce Banner's alter-ego is currently creating more young fans with the HULK AND THE AGENTS OF S.M.A.S.H. series on Disney XD, and has maybe had the most onscreen appearances of any Marvel entity to date if you count the Bixby/Ferrigno series/TV movies. Even the two HULK movies, which weren't universally beloved by any means, still managed to score some bank at the box office, so I'll bet the Marvel dudes and dudettes have at least discussed the possibility of bringing him back, both guns blazing (and by guns, I obviously mean obscenely-large biceps).
We still don't know what flick Marvel has lined up for the already-announced release date of May 5th, 2017, so a new Hulk movie could very well be it. If not, Phase Three will still have one or two more additional solo movies before the next omnibus tentpole (following their previous pattern), so until we officially hear the rest of their slate, keep your ears close to the ground for rumblings of another onscreen Hulk adventure.
But, before you get too excited, I wouldn't expect PLANET HULK just yet. Give 'em time.