If the characters were casted as the right age, I don't think it would be an issue. I didn't see anyone start to ship Lucy and Tumnus after the movie because their ages were different enough, so I think that could work for Rilian and Jill. Unfortunately, Hollywood typically casts teenagers to play children and younger people to play older people, so I don't think that's something we can count on.
The only real romantic implication between Rilian and Jill is when he calls her "sweetheart" and he may compliment her looks at one point (I can't remember exactly) but I always took that as him being kind of a jerk in his enchanted state. For example, no one thinks Haymitch is flirting with Katniss when he calls her "sweetheart" and stuff like that because it's just Haymitch being a jerk.
I think Hollywood will either embrace the ship and possible love triangle (which is not canon in any way) or alter the text to remove any implications. Unfortunately, nowadays any relationship between a boy and a girl in Hollywood is considered to be romantic, so in following the latter we could expect them to make Eustace a girl. (Just kidding.) I think that now we say that we hate the "Jillian" (or whatever it's called) ship, but there are people that ship Suspian now after PC. I'm sure a lot of fans will dislike it, but there are people that ship it already or will ship it after seeing it play out in the movie. I think most people hate the idea now, but the percentage of Narnia fans that hate it now will probably go down a bit if the movie does the ship and the triangle.