Emcee, if it's meant to happen eventually, then it'll happen. My sister was just good friends with this fella for years and years and years, now they're married. They've just had their first biological child together, but I get warm fuzzies every time he refers to my sister's first child as his daughter. Truly he understands the difference between being a father and being a daddy. :3
But on the other hand, it doesn't have to happen at all! You might both wake up one day and find yourselves in the right place for it. You might just as likely continue as you have been doing. Don't ever go anywhere with it that makes you uncomfortable, but *IF* it might move on of its own volition, don't necessarily fight it either.
Awww, everyone's going out. Ah well, at least I'll be able to step away from the PC and do something else (for, like, half an hour, then it's bedtime

).