Sorry, not even the Hulk can disentangle himself from the paper trail that disinclines Disney/Marvel from making another Hulk movie — even though both Disney and Universal (which gets a cut of any such movie) would still probably make money hand over fist from it. Pity, that.
Oh, So That’s Why Marvel Hasn’t Made Any More Hulk Movies
It seems completely obvious in retrospect, but it took a random interview with Mark Ruffalo to explain the likely reason why there’s been no solo Hulk movie yet — it’s Universal’s fault.