Yes, I think it is definitely meant to show that
Tony Stark did propose, but in the most Tony Stark-ish way possible.
In fact, I don't think there was any ambiguity in the scene. I'll admit that it was rather sudden, considering that the last we heard about Pepper and Tony's relationship was that they were taking some time apart. I can't say that I have any evidence from the comics to back up my assertion either. In fact, in the comics, even though Pepper had feelings for Tony at one time, she eventually ended up marrying Happy, Tony's chauffeur.
However, I think others will agree with me when I say that it is fairly obvious from Pepper and Happy's reaction in the movie that Tony proposed to Pepper. Given the context, there is no other announcement to make to the reporters, and he did give her a ring after all. You have to keep in mind that Tony Stark has one of the biggest egos in the MCU, and I highly doubt that he would propose in the traditional fashion of getting down on one knee. Every action Tony makes is deliberate and taken with command. He's used to giving orders, and I think it is unlikely that he would ever ask Pepper to marry him. Rather, it seems to follow his personality that he would "allow" Pepper to finally marry him.