I have two boys aged 6 and the 3 and they are wonderful!!!!
I won’t go in to all the details but with my second I was sure it was a girl, I kept imagining what my daughter would be like, and then when we found out at 20 weeks that it was another boy I felt really disappointed. It wasn’t that I didn’t want another son specifically, it was just the fact that I would never have a daughter as this was going to be our last baby.
However....
Having two boys has been amazing!!! They are so loving towards each other that it makes my heart melt - they are each other’s best friend and have to do everything together!
They have bunk beds (they were adamant they wanted to share as opposed to having their own room) and most mornings when I check up on them, the eldest had crept in with the youngest and they’ll be fast asleep together.
When they sit on the sofa they practically sit in each other’s laps and they just cuddle up and hold hands.
They are always telling each other they love each other and if one of them is going out (for example when DH takes the youngest somewhere) they won’t be separated until they’ve had a kiss and cuddle goodbye.
Honestly, I can’t tell you what a wonderful and special relationship they have.
Yes there is noise, mess and occasional fights, but that is far, far outweighed by how much they love each other. Noise, mess and fighting will occur no matter what sex any siblings are......so I would lose the idea that that scenario is only applicable to having two boys 
In hindsight I am so, so, glad I had a second boy. They have the same interests, like the same cartoons and films, they love playing with the same kind of toys and in general their characters and personalities are so, so alike. When I see them playing with each other and chatting away and being joined at the hip my heart could explode with love.
Do I think my oldest son would have had such a close and loving relationship with his sibling if I’d had a girl? I honestly don’t think so.
Having a daughter would have been nice for me, but having a second son has been
wonderful for my eldest boy. In my personal opinion, I do think that as siblings reach into teenage years and adulthood, they are more likely to remain close and play a main role in each other’s life if they are the same sex.
When I look at them now, I’m so happy my second baby was a boy and I love them both with all my heart.
My husband is into his sport, my eldest is too and I have no doubt my youngest will be too - however, all I see there, when they trot off to football matches, and scream happily at the rugby on the TV is the wonderful, close relationship they have with their dad. My boys are both very much mummy’s boys (especially the eldest) so I’m happy they have this interest with their dad so it’s just something for the three of them.
Do I worry about being pushed out as they get older......not at all. I know they will always love me no matter how much they love sport and I hate it. Their younger years will most likely be mine, and their teenage years are most likely to be their dads, but I’m fine with that. They will grow up to be individuals and if they love sport then that’s fine - we can’t force our children to choose the same interests that we have just so we don’t feel left out or feel like we are being forced to participate in something we aren’t particularly fond of.
My eldest plays golf and I will admit I get bored stiff watching him.....most time I don’t even go to his lessons, but we have such a close relationship in other ways that it’s a total non-issue that I don’t want to watch him hit a ball around. That’s his dad’s domain. 
If you do have another boy, rather than focus on the perceived negatives, just think of all the wonderful things your two boys will be able to get up to with each other.
If I got pregnant again I can honestly say I’d be praying for another boy because I can barely cope with the love I have for the way my current two are together so I can’t envisage how amazing it would be to throw another brother into the mix.
Honestly OP - don’t be anxious about the possibility it may be a boy because if it is, you are hopefully going to provide your current son with a potentially very special sibling relationship.