Well as I said, avatar makes the romance just too obvious, even at the end of season 1, it was only the start of the series. Just cause Mako and Korra were together at the end of the first season didnt mean smooth sailing for another 3.
Pairing fans will be crying but this is why I choose not to ship anything in avatar, its just too obvious and maybe a bigger bloodbath than Naruto. Even then, the way it was ended, it obviously leaves both the possibly of them going back together again once more mature or its a done deal and makorra is dead in the dirt. The way they did this is so that its left those shipping makorra, just obviously it has a future or it doesn't even with the ending this season. At this point, even if it does come back I honestly would not be surprised. Mako and Korra have had impacts on each other and the writers have used fluctuating relationships many times even in the last airbender series. Theres no suprise that something would come up again between Mako and Korra, but the extent of it being done or not is something left waiting to be revealed. Otherwise the writers are just obviously going to stick Mako with Asaumi, just having a spare one right then and there, ya know, too convinent? Least this alt setup has had development unlike NH in Naruto. Where ATLA was more direct with love, the writers are outright tormenting the poor pairing fans with this one. I mean sheesh, it was obvious this season there would be issues between Mako and Korra, but the nature of the writers and just having another pairing for Mako, its just too obvious, either Mako-Korra resurfaces later when they are more mature or they have a shared conflict again like the equalists or its just going to be Mako-Asaumi. Both of these vary however when other new characters come in.
But this is why I don't ship anything in avatar, its too obvious and its just a web of torment, people think Naruto pairing is intense? The manga team in naruto doesn't go out of their way to do stuff like the avatar team does, in naruto the anime and spin-off/other media teams do but that is just filler, hell thats why the avatar writers took potshots at the Zutara crowd in the ember island players. Maybe the end of Makorra this season was just in spirit again them hating zutara? As I said, either Makorra comes back later or its just Mako and Asaumi. The writers make this too obvious but they arn't going to go the full simple open route way either, obviously Mako-Asaumi cannot just happen and should have its own issues as plots move on, but seriously, the base point is the avatar writers really stink at trying to keep love suspenseful, its wide open and either something happens or it doesn't.
Seriously, unlike Naruto's wiki or pairings wiki, the avatar wiki actually has a page dedicated to shipping. While it seems peaceful, there is a lot of blood underneath all that text.