First of all, the independence battle is also the battle of two political clans in Montenegro, each accused of ties to organized crime (the currently ruling, pro-independence one of a hand in cigarette smuggling to the EU, the other of ties to the Milošević clan and allied mafiosi). The not that great majority already implies a strongly divided community.

Second, the EU negotiated a limit of 55% as threshold for the vote to be valid - and the actual result got too close for the losing side to not feel robbed.

Third, national identities are a hazy thing - this is very much true at present in Montenegro, which you should consider before taking any numbers on a "Serbian minority in Montenegro" at face value. As Wikipedia correctly states:

Montenegrin and Serb identities are not exclusive and the size of each group varies with each census, due to political events and as people view themselves, on balance, as more one than the other. A "Montenegrin" may view himself as a "Serb" as well, and vice versa. Of course, in both groups there are those who view themselves as belonging to one group exclusively.

Outside, over 270,000 citizens of Serbia have Montenegrin citizenship. Around 69,000 of them are Montenegrins, while others are mostly Serbs.

Indeed Milošević himself was a Montenegrin. There'll be now an identity crisis affecting much more than at the time of the Yugoslav breakup.

And, fourth, with the last theme of expats in Serbia, we arrive at the first very big problem. In the EU-negotiated rules of voting, the currently ruling pro-independence side got though that expats can't vote in Serbia (but they can everywhere else). While thousands of Montenegrings travelled with buses back to Montenegro to vote, enough remained in Serbia for the losing camp to feel the real majority who was robbed in advance. (They will also blame the EU.)

Now watch these two maps - the tentative Wikipedia map of ethnic majorities in each district, and below it Migeru's map¹, showing the strength of the pro-independence side (blue=loss by a high margin, red=win by a high margin, purple(circle)=winning margin of 55%):

Fifth, a further complication you see comparing the above two maps is that in the districts with ethnic-Bosnian or Albanian majority, the pro-independence side won with a landslide - with generally much narrower results elsewhere. This may result in the losing anti-independence side to pick on the ethnic minorities as culprits for their loss.

As an extra risk factor, the current events could affect other simmering issues like the status of Kosovo, Bosnia, and who knows, further splintering might come (for example the said Bosnian regions of Montenegro, Sandjak).