If this goes fully mainstream, these are some possible things that may happen. (Just random thoughts)

1. Guys wont only be divided into "boobs-guys" and "ass-guys", but also "belly-guys". (I don't know why there are no "feet-guys" yet).
2. Pregnant bellies / bumps will become fully sexualized (even if not every guy has the fetish), and so it will become WAY harder or virtually impossible to touch or rub them casually. Touching bellies in public will be seen as public indecency (the same way touching a girl's breasts or butt is). Hell, touching / rubbing a pregnant woman's belly may be considered "2nd base" already.
3. It will become WAY more awkward for relatives and family to touch the bellies due to the sexualization of pregnancy.
4. Girls will definitely take advantage of being pregnant to get their way (get attention, become Instagram / social media famous / do porn, etc)
5. Pregnant bellies / bumps will start appearing everywhere - especially in marketing and advertising (the same way some companies use random images of boobs and butts to sell their products.)
6. Pregnant girls may become more stuck up and conceited because they know many guys like it. Girls that weren't so attractive before getting pregnant may get a confidence boost from their growing bellies.
7. Some girls will accuse guys of staring at their bellies (Excuse me, my eyes are up here!)
8. Guys with pregnant girlfriends or wives will be more paranoid due to the attention their partners are getting.
9. Pregnant will become an official category in porn (I wonder why it isn't yet)
10. More pregnant escorts (Yes please)
11. More pregnant strippers (Yes please)
12. Legit dating sites for pregnant women (Not like all the fake ones around now)
13. Some women will find a legit way to make money by becoming a surrogate and then doing porn / escort work / modeling while pregnant. (Just imagine how much money they'd be raking in)
14. Sports Illustrated / Maxim / Playboy / etc will make issues that only feature pregnant women.

Anything else?

A lot of these already exists:

1. There's already "belly-guys" in the form of BBW lovers.

4. Already happens

6. They're more stuck up in general due to their messed up hormones.

8. In general this happens, pregnant or not.

9. Most major porn sites and clip stores that I've been to have a pregnant category

13. Already happening. I mean how else would you explain the camgirls and custom clips that pop up in this site?

.

Number 4: We are already there.

Number 6: There already

Numbers 10-12: I really want to see become legit and rise up better than what there currently is.

Number 13: Unless you mean it becomes more popular then, yes otherwise we are there as we speak. The Porn side of it & surrogacy is there and rising.

Number 14: I can definitely see happening. I do see Playboy doing more of it than when Ivanka Trump did it, while pregnant. I also see these magazines making special editions to their collections.

15. Maybe more commercials that are centered around pregnant women and pregnancy
16. Maybe with TV Shows, I think that they should take a page out of Secret Life of the American Teenage where the whole show is dedicated to pregnancy and each season it revolves around a different character dealing with pregnancy. Not like the 16 & Pregnant or Teen Mom cause I think with those shows we exhausted the idea of Teen Pregnancy & Young Moms.
17. More movies based on Pregnancy than the few that are out there and less of the movie called What to Expect When Expecting