It would be pretty pointless anymore. It's just that when the series started as it did, with the boy and the girl sharing a secret and working together for something, trusting each other and having great fun, it seemed like it would naturally develop into romance. In the end, though, this was a story about Akiba's growth as a person. He had already his hands full with other things, so he barely ever even thought about anything romantic. Really disappointing in my opinion, but considering his personality, this might be far more realistic.
Shibuya, of course, could have turned this into a romance, but she didn't. All in all I don't think her character was developed all that well during the series. I'm not saying that in the sense of "since there was no romance, Shibuya failed". It's just that she hardly changed at all during the series. Her whole role was, more or less, to help Akiba develop and get rid of his fears. Shibuya herself is still exactly the same she was at the beginning. Nothing in particular changed in her life, either. Not that it wouldn't be realistic. A bit too much realism for my tastes, perhaps.