We do know that the father is going to be a complicated character, as that’s the way he was described previously – but exactly how this will reflect on his relationship with Sherlock remains a mystery, and fans have been actively speculating on the different implications of that situation.
It’s also worth noting that Sherlock will be going through some severe issues of his own, dealing with the possibility of a suspension after he allowed himself to beat up Oscar like that, and even though that would certainly make things more complicated for his character, it’s also a somewhat expected development for most fans.
After all, it wouldn’t make much sense for the writers to just leave that part of the story untouched, and there will definitely be some repercussions for Sherlock – which, combined with the difficulties he’ll face due to the addition of his father to the picture, should make things quite messy for him.
Let’s hope that there will still be some fun, lighthearted moments in the new season to make up for all of the drama that’s coming up on the horizon, as otherwise fans might find themselves too turned off from the show to continue watching it throughout season 4. Which would be sad, as it’s definitely one of the productions with the strongest potential on the screen right now, and should be developed even further.